UCDP/PRIO Armed Conflict Dataset Codebook
Version 22.1
Uppsala Conflict Data Program
Department of Peace and Conflict Research
Uppsala University
Centre for the Study of Civil Wars
International Peace Research Institute, Oslo

This version compiled and updated by Therese Pettersson (2022)

When using this data, please always cite:
Gleditsch, Nils Petter; Peter Wallensteen, Mikael Eriksson, Margareta Sollenberg & Håvard Strand(2002) Armed Conflict 1946–2001: A New Dataset. Journal of Peace Research 39(5): 615–637.
Davies, Shawn, Therese Pettersson & Magnus Öberg (2022). Organized violence 1989-2021 anddrone warfare. Journal of Peace Research 59(4).
When appropriate, also cite this codebook: Pettersson, Therese (2022) UCDP/PRIO Armed
Conflict Dataset Codebook v 22.1 (https://ucdp.uu.se/downloads/).
Always include the Version number in analyses using the dataset. When referring to the dataset,make sure to use the correct name: the UCDP/PRIO Armed Conflict Dataset.

Contents
1

Introduction .................................................................................................................................... 3

2

Definition of armed conflict ........................................................................................................... 1
2.1

State-based Armed Conflict................................................................................................... 1

3

Variables in the Armed Conflict Dataset ...................................................................................... 3

4

Additional information on variables in the dataset ....................................................................... 7
4.1

Location .................................................................................................................................. 7

4.2

Incompatibility ........................................................................................................................ 8

4.3

Start dates temporal precision ............................................................................................... 8

4.4

Episode end dates temporal precision .................................................................................. 9

4.5

System Membership Description........................................................................................... 95

Missing data .................................................................................................................................. 11

6

Version Name Convention.......................................................................................................... 11

7

References .................................................................................................................................... 12

Appendix 1 List of System Members Since 1946 ............................................................................... 13

1 Introduction
This document describes the UCDP/PRIO Armed Conflict Dataset, a joint project between the
Uppsala Conflict Data Program (UCDP) at the Department of Peace and Conflict Research,
Uppsala University and the Centre for the Study of Civil War at the International Peace ResearchInstitute in Oslo (PRIO). The first release of the Armed Conflict Dataset was prepared at PRIO in
2002 in close collaboration with researchers at UCDP and the Departments of Sociology and
Political Science and Geomatics at the Norwegian University of Science and Technology (NTNU).
For a description of the division of labor in creating the database, see the first footnote in thearticle presenting the dataset, Gleditsch et al. (2002: 615). This footnote also lists the financial
sources of support for the entire project and credits for comments and advice received along theway.
The dataset is available for download from http://www.pcr.uu.se/research/ucdp/datasets/.
Both UCDP and PRIO offer a range of other datasets, compatible with the UCDP/PRIO dataset.
Of special importance is the UCDP Dyadic dataset, which is based on the UCDP/PRIO Armed
Conflict Dataset, but goes beneath the conflict level and focuses on different dyads within eachconflict. Further compatible datasets can be found on both PRIO’s and UCDP’s web pages.
This is version 22.1 of the codebook and associated documents. For our policy on version
labeling, see Section 6 below, and for a complete history of earlier versions see the document
called Version History. For further comments and suggestions on the data and the codebook,please communicate both to ucdp@pcr.uu.se and to jpr@prio.no.
Earlier versions and definitions:
Lotta ThemnérPeter Wallensteen
Birger Heldt
Margareta Sollenberg
Mikael Eriksson &Stina Högbladh
Uppsala Conflict Data Program (UCDP)
Håvard StrandHåvard M. Nygård
Halvard Buhaug
Joachim Carlsen
Nils Petter GleditschHåvard Hegre
Christin M. Ormhaug &Lars Wilhelmsen
International Peace Research Institute, Oslo (PRIO)

2 Definition of armed conflict
The main unit in this dataset is a “State-based Armed Conflict” as defined by UCDP. 1 Thisdefinition is presented unabridged in Section 2.1. Each conflict is listed in the database and given aunique ID code. The temporal aspect of a conflict is not addressed by this definition; hence, two
conflict episodes over the same incompatibility will be assigned the same ID regardless of the time
separating them. See below for further clarifications.

2.1

State-based Armed Conflict

UCDP defines state-based armed conflict as: “a contested incompatibility that concerns
government and/or territory where the use of armed force between two parties, of which at least
one is the government of a state, results in at least 25 battle-related deaths in a calendar year.”
The separate elements of the definition are operationalized as follows:(1)Use of armed force: use of arms, resulting in deaths.
(1.1) Arms: any material means, e.g. manufactured weapons but also sticks, stones, fire, wateretc.
(2)25 deaths: A minimum of 25 battle-related deaths per year and per dyad (see Item 3.3 in thisdefinition) in an incompatibility.2(3)Party: A government of a state or any opposition organization or alliance of organizations.
UCDP distinguishes between primary and secondary parties. Primary parties are those thatform an incompatibility by stating incompatible positions (see Item 5 in this definition). At least
one of the primary parties is the government of a state.
Secondary parties are states that enter a conflict with troops to actively support one of the
primary parties. The secondary party must share the position of the primary party it is
supporting in the incompatibility.
(3.1) Government: The party controlling the capital of a state.
(3.2) Opposition organization: Any non-governmental group of people having announced a namefor their group and using armed force to influence the outcome of the statedincompatibility (see Item 5 in this definition). The UCDP only deals with formallyorganized opposition. The focus is on armed conflict involving consciously conducted
and planned political campaigns rather than spontaneous violence.
(3.3) Dyad: A dyad consists of two conflicting primary parties. At least one of the primaryparties must be the government of a state. In interstate conflicts, both primary parties

1For a more in-depth discussion on definitions, see http://www.pcr.uu.se/research/ucdp/definitions/.
2 Note that an incompatibility involving two opposition groups, each involved in clashes with the government resulting in 20 deaths, would not berecorded as a conflict (neither dyad reached the minimum casualty threshold), whereas an incompatibility involving a single opposition group thatcaused 25 battle-deaths would be included in the dataset.

1

are state governments.3 In intrastate and extrasystemic conflicts, the non-governmental
primary party includes one or more opposition organization(s). A conflict can include
more than one dyad. If e.g. a government is opposed by three rebel groups over thesame incompatibility, the conflict is made up of three dyads. Note that secondary
parties (i.e. intervening states supplying troops to one of the primary parties) do notlead to the formation of additional dyads.
(4)State: A state is an internationally recognised sovereign government controlling a specificterritory or an internationally unrecognised government controlling a specified territory whosesovereignty is not disputed by another internationally recognized sovereign government
previously controlling the same territory. See Section 4.5 for details on the sample of countries
covered by this definition.
(5)Incompatibility concerning government or territory: The incompatibility, as stated by the parties,
must concern government and/or territory.
(5.1) Incompatibility: The stated general incompatible positions.
(5.2) Incompatibility concerning government: Incompatibility concerning type of political system,
the replacement of the central government, or the change of its composition.
(5.3) Incompatibility concerning territory: Incompatibility concerning the status of a territory, e.g.
the change of the state in control of a certain territory (interstate conflict), secession orautonomy (intrastate conflict).

3With three exceptions, the primary parties in interstate conflicts consist of only one actor on each side (and thus only constitute one dyad). See

description of Location (Section 4.1) below for further information on these cases.

23 Variables in the Armed Conflict Dataset
The observation (or unit) in the dataset is the conflict-year. Each conflict is listed in all years where
fighting in one or more dyad(s) caused at least 25 battle-related deaths.4
The calendar year is the basic unit of every observation. Thus, if a conflict during the period June–
September results in 30 casualties, that year will be recorded as a year of conflict. However, if thesame number of casualties occurred in the period November–February and the conflict failed toreach the threshold of 25 battle-related deaths in either calendar year, neither year will be coded
as in conflict. This has a number of consequences that will be discussed below. Start dates
frequently refer to years prior to the first calendar year of a conflict, as the start of a conflict might
be in a year with less than 25 fatalities. Small conflicts might not be included. Certain observations
might be based on a single event, such as the Omagh bombing in Northern Ireland in 1998, which
exceeded the minimum threshold for armed conflict.
Variable nameContent

Type

conflict_id

The unique identifier of the conflict.

Integer

location

The name of the country/countries whose
government(s) has a primary claim to the incompatibility.
Note that this is not necessarily the geographical locationof the conflict. Further information on how location isinterpreted can be found below, in section 4.1.
If multiple countries are listed, this is comma separated.

Stringside_aThe name of the country/countries of Side A in a conflict.

StringAlways the government side in intrastate conflicts. Notethat this is a primary party to the conflict.
side_a_id

The unique identifier of the actor on side A.

Integer

Note that in contrast with older versions of UCDP
datasets, this variable is NO LONGER the Gleditsch andWard state identifier (GWcode or GWNo). Use thegwno_a variable instead.
side_a_2nd

side_a_2nd lists all states that enter a conflict with troops String
to actively support side A. By definition, only independent
states can be a secondary party in conflict.

4 This is in contrast to Version 2.1 (and earlier versions) of the dataset. The previous formulation read ‘The observation (or unit) in the database is a

conflict-year, a subconflict, or a subset of either over a period of time where no element in the definition described in Section 2 is changed. Eachconflict is likely to include several observations. This definition of the primary unit made sense in the text lists that preceded this dataset, where
space was an important issue. The data structure was kept in order to stay compatible with previous versions. But while this might be advantageous
to old users, it has confused a number of new users. The annual data structure therefore replaced the old structure in Version 3.0 (2005).

3

A secondary warring party on side A shares the position in
the incompatibility with Side A in the conflict.
side_a_2nd does not need to meet the 25 battle-related
deaths criterion to be included in the dataset; an active
troop participation is enough.
Comma separated if multiple.
side_b

Identifying the opposition actor or country/countries of Stringside B in the conflict. In an intrastate conflict, this includes a
military opposition organization. Note that this is a
primary party to the conflict.
Comma separated if multiple.

side_b_id

The identifier of each of the actors on side B in the String
conflict.
Note that in contrast with older versions of UCDP
datasets, this variable is NO LONGER the Gleditsch andWard state identifier (GWcode or GWNo) if the conflictis interstate and Side B represents a country. Use thegwno_b variable instead.
If more than one opposition organization or state is
involved in a conflict, this is a comma-separated list ofvalues.

side_b_2nd

side_b_2nd lists all states that enter a conflict with troops String
to actively support side B. By definition, only independent
states can be a secondary party in conflict.
A secondary warring party on side B shares the position in
the incompatibility with Side B in the conflict.
Side_b_2nd does not need to meet the 25 battle-related
deaths criterion to be included in the dataset; an active
troop participation is enough. Note that when there ismore than one opposition organization listed in an
intrastate conflict, the dataset does not provide
information on which of these groups the state coded as
Side B Secondary is supporting.
Comma separated if multiple.

incompatibility

The main conflict issue identified per the UCDP Integer
definitions:
1= Incompatibility about territory
2= Incompatibility about government
3= Incompatibility about government AND territory
Further information on how incompatibility is interpreted
can be found below, in section 4.2

4

territory_name

The name of the territory over which the conflict is fought, String
provided that the incompatibility is over territory.
In case the two sides use different names for the disputed
territory, the name listed is the one used by the opposition
organisation. One reason for this is that this is most often
the name that the general public recognises. Anotherreason is that there are cases where the disputed
territories do not have an official name.

year

The year of observation (1946-2021).

Integerintensity_level

The intensity level in the conflict per calendar year. The Integer
intensity variable is coded in two categories:5
1= Minor: between 25 and 999 battle-related deaths in agiven year.
2= War: at least 1,000 battle-related deaths in a given
year.

cumulative_intensity

This variable takes into account the temporal dimension of Integer
the conflict. It is a dummy variable that codes whether the
conflict since the onset has exceeded 1,000 battle-related
deaths. For conflicts with a history prior to 1946, it does
not take into account the fatalities incurred in preceding
years. A conflict is coded as 0 as long as it has not overtime resulted in more than 1,000 battle-related deaths.
Once a conflict reaches this threshold, it is coded as 1.

type_of_conflict

One of the following four types of conflict:Integer
1 = extrasystemic (between a state and a non-state groupoutside its own territory, where the government side isfighting to retain control of a territory outside the statesystem)2 = interstate (both sides are states in the Gleditsch andWard membership system).
3 = intrastate (side A is always a government; side B isalways one or more rebel groups; there is no involvementof foreign governments with troops, i.e. there is noside_a_2nd or side_b_2nd coded)
4 = internationalized intrastate (side A is always agovernment; side B is always one or more rebel groups;
there is involvement of foreign governments with troops,
i.e. there is at least ONE side_a_2nd or side_b_2nd
coded)

5 In earlier versions of the UCDP/PRIO dataset, the intensity variable contained three categories: minor, intermediate and war. The intermediate

category was defined as “more than 25 battle-related deaths per year and a total conflict history of more than 1000 battle-related deaths, but fewer
than 1000 per year.” Thus, the variable included a temporal dimension into the intensity coding. However, as many users incorrectly interpreted
the variable as ordinal, it was decided that the intermediate category should be represented by a separate dummy variable denoting cumulative
intensity.

5

start_date

The date, as precise as possible, of the first battle-related Date(YYYY-MM-DD)
death in the conflict.
The date is set after the conflict fulfils all criteria requiredin the definition of an armed conflict, except for thenumber of deaths.6

start_prec

The level of precision for the initial start date.

Integer

The values are explained in section 4.3
start_date2

The date, as precise as possible, when a given episode of Date
conflict activity reached 25 battle-related deaths in a year. (YYYY-MM-DD)
Thus, for each episode of a conflict, a new Startdate2 iscoded. In case precise information is lacking, Startdate2 isby default set to 31 December.
An episode is defined as continuous conflict activity.
Consequently, a new episode is coded whenever a conflict
restarts after one or more year(s) of inactivity.

start_prec2

The level of precision for startdate2.

Integer

The values are explained in section 4.3
ep_endA dummy variable that codes whether the conflict is Integer
inactive the following year and an episode of the conflictthus ends. If the conflict is inactive the following year(s),this variable is coded as 1. If not, a 0 is coded. For thelatest year in the dataset, it is unknown whether the
conflict will be recorded as active or inactive in thefollowing year, and the variable is always given the code 0.

ep_end_date

This variable is only coded in years where ep_end has the Datevalue 1. If a conflict year is followed by at least one year of (YYYY-MM-DD)
conflict inactivity, the ep_end_date variable lists, as precise
as possible, the date when conflict activity ended.

ep_end_prec

The level of precision for episode end.

Integer

The values are explained in section 4.4

6 In some cases, the initial fatality occurs in a year prior to the first year of activity. For instance, in the conflict inEthiopia over the territory Eritrea (conflict ID 275), the first battle-related deaths occurred in September 1961. During
the remaining months of 1961, the conflict did not reach the required 25 battle-related deaths threshold and theconflict is thus coded as inactive in 1961. 25 battle-related deaths were not recorded until three years later. In earlyversions of the dataset, the start_date was assigned a new value whenever there was a complete change on side B.
Departing from the new start_date users could break a conflict up into different periods. However, with theintroduction of episodes in the UCDP/PRIO dataset and with the launching of the new UCDP Dyadic dataset thisbecame redundant.

6

gwno_a

The Gleditsch and Ward country codes of side_a.

StringComma separated if multiple.
gwno_a_2nd

The Gleditsch and Ward country codes of side_a_2nd.

StringComma separated if multiple.
gwno_bThe Gleditsch and Ward country codes of side_b.

StringComma separated if multiple.
gwno_b_2nd

The Gleditsch and Ward country codes of side_b_2nd.

StringComma separated if multiple.
gwno_loc

The Gleditsch and Ward country codes of theincompatibility.

StringComma separated if multiple.
regionThe region of the incompatibility:

String

1 = Europe (GWNo: 200-399)
2= Middle East (GWNo: 630-699)
3= Asia (GWNo: 700-999)
4= Africa (GWNo: 400-626)
5= Americas (GWNo: 2-199).
versionThe version of the dataset: 22.1

Float

4 Additional information on variables in the dataset
4.1

Location

Location is defined as the government side of a conflict, and should not be interpreted as thegeographical location of the conflict.
• For intrastate and internationalized intrastate conflicts, only one country name is listed. Thisis the country whose government or territory is disputed. For certain conflicts, such as
Kurdistan, the disputed territory is divided between different countries. Following ourdefinition, we have coded separate conflicts for each country.
• For interstate conflict, all primary parties are listed in the Location field. Even if several
governments are involved in the conflict, only countries that fulfil the inclusion criteria forprimary actors are listed here. This normally means that two countries are listed, but there
are four notable exceptions: In the Arab-Israeli war of 1948–49 as well as the Suez war of1956, the war in Afghanistan in 2001 and the war in Iraq in 2003, there are more than two
primary parties to the conflict.
• For extrasystemic conflicts, Location is set to be the disputed area, not the government of
the colonial power. Since the Location field in these conflicts by default does not indicate
7members of the international system, it constitutes an exception from the definition
presented in Section 2.

4.2

Incompatibility

As a country can experience several simultaneous conflicts, it is essential to differentiate between
them. As described in Section 2.1, UCDP collects information on conflicts where theincompatibility, i.e. the general incompatible positions, concerns either government, territory or
both. Early versions of the UCDP/PRIO dataset only contained two incompatibility categories,
territory and government. Conflicts that concerned both territory and government were assigned
to their primary incompatibility. From Version 4-2007, the incompatibility has been coded in three
categories:
1. Territory
2. Government
3. Government AND Territory
Note that the incompatibility expressed in terms of government or a specific territory is crude in
the sense that possible underlying incompatibilities are not considered. In other words, the statedincompatibility is what the parties are (or claim to be) fighting over, but it says nothing about why
the parties are fighting.
While a state can only experience one intrastate conflict over government in a given year, thatsame state can simultaneously be a primary party to one or more interstate conflicts over
government and/or territory. In the case of intrastate territorial conflicts, multiple conflicts can berecorded over different territories in a state in a given year.

4.3

Start dates temporal precision7

The Start date is coded as precisely as possible. For certain conflicts we can pinpoint the start of
the armed conflict down to a single event, taking place on a specific day. For other conflicts, this is
not possible, due to lack of precise information. The start precision is coded to highlight the levelof certainty for the date set in the start_date variable.
1. Day, month and year are precisely coded; we have good information on the event.
2. Day is assigned; month and year are precisely coded. The assigned date can either be one ofseveral events that can be classified as the first; it can be the last day in a period whenseveral fatalities have been reported jointly or it can be an event that different sources claim
occurred on different dates.
3. Day is unknown; month (or a period of 30 days, not necessarily a calendar month) and year
are precisely coded. The day is known to be in a given month or 30 day-period, but we are
missing information on an exact date. Day is then set to the last day of the period.
4. Month is assigned; year is coded precisely.
7 The format for coding start dates has been slightly changed in 2014, and then again in 2017, in an attempt to provide

more detailed information.

8

5. Day and month are unknown, year is coded precisely. Day and month are set as precisely as
possible. For example, if an event is known to have taken place sometime between January
and August, the date is coded as 31 August of the coded year, with a precision of 5.
6. Year is assigned. There is a wide disagreement between different sources, so that not evenyear can be coded precisely. The start year is assigned based on subjective judgment. Day
and month are set as precisely as possible. For example, if an event is known to have takenplace sometime between January and August in an assigned year, the date is coded as 31
August, with a precision of 6.
7. Year is missing. No reliable information on the start year is available. Day and month are set
as precisely as possible for the first year of recorded activity. For example, if an event is
known to have taken place sometime between January and August in an assigned year, thedate is coded as 31 August, with a precision of 7.

4.4

Episode end dates temporal precision

The end_date is coded as precisely as possible. For certain conflicts we can pinpoint thetermination of the armed conflict down to a single event, taking place on a specific day. For otherconflicts, this is not possible, due to lack of precise information. The end_prec is coded to highlightthe level of certainty for the date set in the end_date variable.
1= Day, month and year are precisely coded; we have good information on the event.
2= Day is assigned; month and year are precisely coded. The assigned date can either be one ofseveral events that can be classified as the last; it can be the last day in a period when several
fatalities have been reported jointly or it can be an event that different sources claim occurred on
different dates.
3= Day is unknown; month (or a period of 30 days, not necessarily a calendar month) and year
are precisely coded. The day is known to be in a given month or 30 day-period, but we are
missing information on an exact date. Day is then set to the last day of the period.
4= Month is assigned; year is coded precisely.
5= Day and month are unknown, year is coded precisely. Day and month are set as precisely as
possible. For example, if an event is known to have taken place sometime between January andAugust, the date is coded as 31 August of the coded year.

4.5

System Membership Description

The definition of a state is crucial to the UCDP/PRIO conflict list, and subsequently also for the
dyadic dataset.
State: A state is:a) an internationally recognized sovereign government controlling a specified territory, orb) an internationally unrecognized government controlling a specified territory whosesovereignty is not disputed by another internationally recognized sovereign government
previously controlling the same territory
The conflict definition, and hence also the dyad definition, is based upon participating
governmental actors of independent states, and the classification of a given conflict rests heavily
9upon the status of the different actors. In order to define the total population of states we use the
Gleditsch & Ward (1999) systems membership definition, which is based on the Correlates of
War project. Gleditsch & Ward include countries with a population of more than 250,000 thathave ‘a relatively autonomous administration over some territory’, and is ‘considered a distinct
entity by local actors or the state it is dependent on’ (Gleditsch & Ward, 1999: 398).
The Gleditsch & Ward definition differs from our original definition in two main ways. First, for
Gleditsch & Ward a state is considered to be a new entity if it is ‘considered a distinct entity by
local actors’ while the conflict definition only recognizes it as a new entity when the ‘sovereignty is
not disputed by another internationally recognized sovereign government previously controllingthe same territory’. Second, the Gleditsch & Ward states all have a population of more than
250,000 while our conflict definition does not prescribe a specific size of the population. In a few
cases, countries with less than 250,000 inhabitants experience conflict or are active as secondary
parties in a conflict. In those cases, we use the Gleditsch & Ward tentative list of microstates. For
example, the microstate Tonga was part of the multinational coalition fighting in Iraq in 2004.
The UCDP/PRIO dataset includes one political entity that lacks a country code (gwno_a is set at 99) as it is excluded from both the Gleditsch & Ward system membership table and the tentative
list of microstates: Hyderabad (Hyderabad vs. CPI and Hyderabad vs. India). In 1947 when
England granted India independence, a cabinet memorandum declared that the Princely States
were free to decide to either join India or Pakistan before August 1947 - or devise their own
sovereign political system for self-governance. Hyderabad declared itself independent on 15
August 1947. The state was populated by approximately 15,000,000 inhabitants. The systemmembership ended when Hyderabad was annexed by India in September 1948, after Winston
Churchill had proposed to the United Nations to consider it as an independent state.
In a couple of cases, the dataset has a different sovereignty date for some countries that haveexperienced conflict:•

Croatia
Gleditsch & Ward: 25 June 1991 (declares independence)
UCDP/PRIO: 27 April 1992 (the new constitution of Yugoslavia)•

Georgia:
Gleditsch & Ward: 6 September 1991 (the USSR’s recognition of Georgia’s declaration of
independence, on 9 April 1991)
UCDP/PRIO: 21 December 1991 (USSR formally ceased to exist)
Comment: While Gleditsch & Ward claim that the USSR recognised Georgia’s
independence on 6 September, this seems to be incorrect. On 6 September, the Soviet
Union recognized the Baltic States’ independence, but not Georgia’s. Instead, the Soviet
Union in early September 1991 refused to discuss recognition of the declaration of
independence.
10

Gleditsch & Ward use a slightly modified version of the COW numbering system. The table inAppendix 1 presents the system membership table that we base our data tables on. These data
are based on Gleditsch & Ward’s 2013 version of the list of independent states.

5 Missing data
The missing data code is -99. However, the dataset does not include unclear conflicts where
information on key variables to the definition of conflict is uncertain or missing. Key variables arethose related to the incompatibility, actors and intensity. In addition, a number of events havebeen identified as potentially in accordance with the criteria for inclusion. These events include
possible new dyads and additional years for active conflicts. Consult the list of unclear cases forfurther information.
The information also varies with regard to the level of precision. For the start date variables, theprecision level is indicated in a separate variable, see section 4.3. Apart from that, the dataset only
includes information when we are quite confident that it is correct. The bias produced by thisapproach is against the inclusion of conflicts in the earlier decades and in the less-developed world.
An armed conflict in a developed country in the 1990s is more likely to be recorded than a conflictin a less developed country in the 1950s.

6 Version Name Convention
In 2017, the version name convention was changed, giving all UCDP datasets the same version
number across the board. This was done so that users more easily can see which UCDP dataset
corresponds with which.
This codebook corresponds to Version 22.1 of the UCDP/PRIO dataset. For every new release,substantial changes will be documented in a separate document. 8 This should be helpful toresearchers trying to replicate a particular study. We recommend that whenever this dataset isused, the version number should be cited.
The version number is a combination of a year and a number. The year refers to when the dataset
is updated with new observations. If there are changes in the data between yearly updates, or if
there are substantial changes in the structure of the dataset, the number behind the year isincremented.

8 http://ucdp.uu.se/downloads/

11

7 References
Gleditsch, Kristian S. & Michael D. Ward (1999) Interstate System Membership: A Revised List of
the Independent States since 1816. International Interactions 25: 393–413.
Gleditsch, Kristian S. Skrede & Michael D. Ward (2013) System membership case description list.
Gleditsch, Nils Petter; Peter Wallensteen, Mikael Eriksson, Margareta Sollenberg & Håvard Strand(2002) Armed Conflict 1946–2001: A New Dataset. Journal of Peace Research 39(5): 615–
637.
Davies, Shawn, Therese Pettersson & Magnus Öberg (2022). Organized violence 1989-2021 anddrone warfare. Journal of Peace Research 59(4).

12Appendix 1 List of System Members Since 1946
StateNum

StateAb StateName

StartYear

2
20
31
40
41
42
51
52
53
70
80
90
91
92
93
94
95
100
101
110
115
130
135
140
145
150
155
160
165
200
205
210
211
212
220
225
230
235
260
265
290

USA
CAN
BHM
CUB
HAI
DOM
JAM
TRI
BAR
MEX
BLZ
GUA
HON
SAL
NIC
COS
PAN
COL
VEN
GUY
SUR
ECU
PER
BRA
BOL
PAR
CHL
ARG
URU
UKG
IRE
NTH
BEL
LUX
FRN
SWZ
SPN
POR
GFR
GDR
POL

1946
1946
1973
1946
1946
1946
1962
1962
1966
1946
1981
1946
1946
1946
1946
1946
1946
1946
1946
1966
1975
1946
1946
1946
1946
1946
1946
1946
1946
1946
1946
1946
1946
1946
1946
1946
1946
1946
1949
1949
1946

United States of America
CanadaBahamasCuba
Haiti
Dominican Republic
Jamaica
Trinidad and Tobago
Barbados
MexicoBelizeGuatemalaHonduras
El Salvador
Nicaragua
Costa Rica
PanamaColombia
Venezuela
GuyanaSurinamEcuador
Peru
BrazilBoliviaParaguay
Chile
Argentina
Uruguay
United Kingdom
IrelandNetherlands
Belgium
Luxembourg
FranceSwitzerland
Spain
Portugal
German Federal Republic
German Democratic Republic
Poland13

EndYear1990

StateNum

StateAb StateName

StartYear

305
310
315
316
317
325
338
339
340
341
343
344
345
346
347
349
350
352
355
359
360
365
366
367
368
369
370
371
372
373
375
380
385
390
395
402
404
411
420
432
433
434
435
436
437

AUS
HUN
CZE
CZR
SLO
ITA
MLT
ALB
SER
MNG
MAC
CRO
YUG
BOS
KOS
SLV
GRC
CYP
BUL
MLD
RUM
RUS
EST
LAT
LIT
UKR
BLR
ARM
GRG
AZE
FIN
SWD
NOR
DEN
ICE
CAP
GNB
EQG
GAM
MLI
SEN
BEN
MAA
NIR
CDI

1946
1946
1946
1993
1993
1946
1964
1946
2006
2006
1991
1991
1946
1992
2008
1992
1946
1960
1946
1991
1946
1946
1991
1991
1991
1991
1991
1991
1991
1991
1946
1946
1946
1946
1946
1975
1974
1968
1965
1960
1960
1960
1960
1960
1960

Austria
Hungary
Czechoslovakia
Czech Republic
Slovakia
Italy/Sardinia
Malta
Albania
SerbiaMontenegro
Macedonia (FRY)
Croatia
Yugoslavia (Serbia)
Bosnia-Herzegovina
KosovoSlovenia
GreeceCyprusBulgaria
Moldova
Rumania
Russia (Soviet Union)
Estonia
LatviaLithuania
UkraineBelarus (Byelorussia)
Armenia
Georgia
Azerbaijan
FinlandSwedenNorwayDenmark
IcelandCape Verde
Guinea-Bissau
Equatorial Guinea
GambiaMali
SenegalBenin
Mauritania
Niger
Cote D’Ivoire

14

EndYear
1992

2006

StateNum

StateAb StateName

438
439
450
451
452
461
471
475
481
482
483
484
490

GUI
BFO
LBR
SIE
GHA
TOG
CAO
NIG
GAB
CEN
CHA
CON
DRC

500
501
510
511
516
517
520
522
530
531
540
541
551
552
553
560
565
570
571
572
580
581
590
600
615
616
620
625
626
630
640

UGA
KEN
TAZ
ZAN
BUI
RWA
SOM
DJI
ETH
ERI
ANG
MZM
ZAM
ZIM
MAW
SAF
NAM
LES
BOT
SWA
MAG
COM
MAS
MOR
ALG
TUN
LIB
SUD
SSD
IRN
TUR

StartYear

GuineaBurkina Faso (Upper Volta)
Liberia
Sierra Leone
Ghana
Togo
Cameroon
Nigeria
Gabon
Central African Republic
Chad
Congo
Congo, Democratic Republic(Zaire)UgandaKenya
Tanzania/Tanganyika
ZanzibarBurundiRwandaSomalia
Djibouti
Ethiopia
EritreaAngolaMozambiqueZambiaZimbabwe (Rhodesia)
MalawiSouth Africa
Namibia
LesothoBotswana
Swaziland
Madagascar (Malagasy)
Comoros
Mauritius
MoroccoAlgeria
Tunisia
Libya
Sudan
South Sudan
Iran (Persia)
Turkey/Ottoman Empire

15

EndYear

1958
1960
1946
1961
1957
1960
1960
1960
1960
1960
1960
1960
of 1960
1962
1963
1961
1963
1962
1962
1960
1977
1946
1993
1975
1975
1964
1965
1964
1946
1990
1966
1966
1968
1960
1975
1968
1956
1962
1956
1951
1956
2011
1946
1946

1964

StateNum

StateAb StateName

StartYear

645
651
652
660
663
666
670
678
680
690
692
694
696
698
700
701
702
703
704
705
710
711
712
713
731
732
740
750
760
770
771
775
780
781
790
800
811
812
816
817
820
830
835
840
850

IRQ
EGY
SYR
LEB
JOR
ISR
SAU
YEM
YPR
KUW
BAH
QAT
UAE
OMA
AFG
TKM
TAJ
KYR
UZB
KZK
CHN
TBT
MON
TAW
PRK
ROK
JPN
IND
BHU
PAK
BNG
MYA
SRI
MAD
NEP
THI
CAM
LAO
DRV
RVN
MAL
SIN
BRU
PHI
INS

1946
1946
1946
1946
1946
1948
1946
1946
1967
1961
1971
1971
1971
1946
1946
1991
1991
1991
1991
1991
1946
1946
1946
1949
1948
1948
1946
1947
1949
1947
1971
1948
1948
1965
1946
1946
1953
1954
1954
1954
1957
1965
1984
1946
1946

Iraq
Egypt
Syria
LebanonJordanIsraelSaudi Arabia
Yemen (Arab Republic of Yemen)
Yemen, People's Republic of
KuwaitBahrain
Qatar
United Arab Emirates
Oman
Afghanistan
Turkmenistan
Tajikistan
Kyrgyz Republic
Uzbekistan
Kazakhstan
China
Tibet
Mongolia
Taiwan
North Korea
South Korea
Japan
India
BhutanPakistan
Bangladesh
Myanmar (Burma)
Sri Lanka
Maldives
Nepal
ThailandCambodia (Kampuchea)
Laos
Vietnam, Democratic Republic ofVietnam, Republic of
Malaysia
Singapore
Brunei
Philippines
Indonesia

16

EndYear

1990

1950

1975

StateNum

StateAb StateName

StartYear

860
900
910
920
940
950

ETM
AUL
PNG
NEW
SOL
FJI

2002
1946
1975
1946
1978
1970

East Timor
Australia
Papua New Guinea
New Zealand
Solomon Islands
Fiji

17

EndYear