# Long Peace

The "Long Peace" is a term for the unprecedented historical period of relative global stability following the end of World War II in 1945 to the present day. The period of the Cold War (1947–1991) was marked by the absence of major wars between the superpowers of the period, the United States and the Soviet Union. John Lewis Gaddis first used the term in 1986, stressing that the period of "relative peace" has twice outlasted the interwar period by now. The Cold War, with all its rivalries, anxieties and unquestionable dangers, has produced the longest period of stability in relations among the great powers that the world has known in the 20th century; it now compares favorably as well with some of the longest periods of great-power stability in all of modern history. The Long Peace has been compared to the relatively-long stability of the Roman Empire, the Pax Romana, or the Pax Britannica, a century of relative peace that existed between the end of the Napoleonic Wars in 1815 and the outbreak of World War I in 1914, during which the British Empire held global hegemony. Since Pax Britannica was interrupted by major power wars and Pax Romana was not on the global scale, some scholars find us living in the most peaceful period of modern time, or even "in the most peaceful era in our species' existence."

## Decline of war

Coining the term Long Peace in 1986, Gaddis warned: One should be exceedingly wary of predicting how long the current era of Soviet-American stability will last. It lasted five more years. Then the Cold War ended causing what the US strategists called "peace shock." The following Defense Planning Guidance expressed a relief: we no longer will focus on the threat of a short-warning Soviet-led, European-wide conflict leading quickly to global war and, perhaps, escalating just as quickly to nuclear war. The world appeared pacified with no mighty Eurasian state or bloc targeting its strategic forces on the West and no great-power war looming in Eurasia. In 1991, the "Doomsday Clock" of the Bulletin of the Atomic Scientists retreated to 17 minutes to midnight, the furthest from midnight the clock has been since its inception and expressing a huge time span for the Bulletin. The same year, US Chairman of the Joint Chiefs of Staff, Colin Powell, expressed his problem: "I'm running out of demons. I'm running out of enemies. I'm down to Castro and Kim II Sung."
Initially, it was thought that the Long Peace was a unique result of the Cold War. However, in the post-Cold War period the same trends continued and strengthened. In 2005, Gaddis concluded that major wars fought between major states had become an anachronism. The post-Cold War peace become called the "New Peace." Wars between leading powers and preparations for such wars have been the driving motor of international politics for centuries. "At the risk of hyperbole," Robert Jervis suggests that turning off this motor is the greatest change in international politics seen in history by 2010.
Initially called debellicisation,the supposed process became better known as the Decline-of-War thesis. Since 1945, it was claimed, the world pacification becomes exponential. The Korea War was one of most intensive during the Cold War but passive relatively to the preceding two centuries: "War had stepped back two centuries to the age of limited war." In the following decades, war overall continued to diminish dramatically, with the year 1991 marking another threshold when the trend gathers momentum.
The Cold War was certainly peaceful compared to the historically unparalleled half century of bloodletting that preceded it, but it was much more violent than anything that has followed. By the 2010s, the research community broadly agreed that the number and deadliness of interstate wars has declined dramatically since the end of World War II, and the incidence of civil wars has declined substantially since the end of the Cold War. The number of battle deaths fell precipitously in the 1990s and 2000s. Taking a longer historical view, international war within the "central system" of states, which had been common since the late 15th century, declined fast after 1945 and reached unprecedented lows after 1990.

## Trend in numbers

The worldwide rate of death from interstate and civil war combined has juddered downward, from almost 300 per 100,000 world population during World War II, to almost 30 during the Korean War, to the low teens during the era of the Vietnam War, to single digits in the 1970s and 1980s, to less than 1 in the 21st century. The number of international wars decreased from a rate of six per year in the 1950s to one per year in the 2000s, and the number of fatalities decreased from 240 reported deaths per million to less than 10. In the 1990s, far fewer people died in wars per year than during the Cold War, and in the 2000s their number dropped twice, hitting the lowest recorded number of 56,000 people in 2008. This was the lowest mark of fatalities per population since AD 1400 to the least. The lack of sufficient data before 1400 precludes knowing whether it was the all-time low.
From 2008 to 2021, war fatalities worldwide rose six times, to 348,000 in 2021. However, contrary to a popular belief, the world became more peaceful in three following years. In 2022, despite the Russian invasion of Ukraine, world fatalities dropped by 4%, to 334,000. The drop was due to the end of the Tigray War, which in 2022 was deadlier than the Russo-Ukrainian War. The next two years, with the latter War raging and the Israel-Hamas war began, the world became more peaceful, with 170,000 people killed in wars in 2023, and 233,000 in 2024.
Civilian fatalities declined even faster. 3 years before the end of World War II, Quincy Wright estimated for modern world "at least 10%" of deaths caused by war including indirect causes, that is, 1.8 billion. On the casualty chart, in the postwar period military and civilian rates combined and military rate only nearly coincide towards the year 2000, meaning civilian fatalities nearly disappeared. In the 21st century so far, wars have not caused mass starvations, or pandemics.
The period also has exhibited more than a quarter of a century of even greater stability and has shown continued improvements in related measurements such as the number of coups, the amount of repression, and the durability of peace settlements. States stopped dying by conquest since 1945. Though civil wars and lesser military conflicts have occurred, there has been a continued absence of direct conflict between any of the largest economies by gross domestic product; instead, wealthier countries have fought limited small-scale regional conflicts with poorer countries. Conflicts involving smaller economies have also gradually tapered off.
Global military spending reached modern-time high in 2024, but per global gross product it remains close to modern-time low. The percentage of the world gross product devoted to military spending has been generally decreasing since World War II. Tallies from the 1960s report military spending rates above 6% of world GDP and in a range from 3.8% to 4.5% in the 1970s and 1980s. It was 4.92% in 1990 (below the Cold War average), reached the lowest recorded in modern history mark of 2.1% in 2014 and 2018, and fluctuates between 2.1 and 2.4% ever since. The 21st-century world has relaxed its military effort and devoted a larger budget for non-military purposes.
The year Gaddis coined the term Long Peace (1986), the world nuclear stockpile was at its all time high of over 70,000 warheads. It decreased to about 12,100 in 2024, or by over 80%. The global military personnel per 100,000 people fell from close to 700 in 1970 to 428 in 2024.
For Jack S. Levy, a substantial conflict has at least 1000 battle deaths per 1 million system's population. There have been 10 such wars during the five-century span of the modern system, one per 50 years on the average. As of 2025, we are 80 years without such a war. Earlier, Bernard Brodie had written on severe lessons of history:
   The recorded history of our civilization is now five or six thousand years old. It is admittedly difficult to conceive of the human race going on for a comparable period in the future without once pulling the stops on the kind of destructive orgy which nuclear weapons now, and no doubt also other instruments in the future, will make possible. But if we could defer the total war for only 50 years, it would surely be worthwhile to do so even if we were only deferring the inevitable.
As of 2025, we defer the total war for 80 years, and not only total or nuclear. In 2011, a chapter was published, entitled "Explaining the 60-year decline in the incidence of international conflict." Besides the drop in casualties, it counts that there has been total decrease in the number of wars between developed states (zero since 1945) and between the major powers (zero since 1954). As of 2025, both zeroes hold. 202 states died since 1800, the most by conquest, but 0 states died by conquest since 1945. According to John Mueller, the "most significant number in the history of warfare: zero." What Pinker describes as the "most interesting statistic since 1945" does not lend itself well to being displayed in a chart. This is because it is a single number—zero: "Zero is the number that applies to an astonishing collection of categories of war" since 1945.

## Research and debate

In his 2011 book The Better Angels of Our Nature, Steven Pinker criticized the approach of counting wars or conflicts because this approach gives equal value to World War II and the Falkland War. He called: "Now let's put the numbers back together, and instead of looking at the number of wars, look at number of deaths, again scaled by world population." Jack Levy finds this approach the best and most widely used measure of the war intensity and in general a standard measure of homicide. The ratio per population per time is added to the formula for the purpose of proportion. Since both the number of casualties and their impact on society are functions of population and army size, a measure of battle deaths relative to population is used and defined as the intensity of war. Many scholars follow the dead-per-population ratio. This approach revealed drastic world pacification. "In fact the famous dream is coming true: the world is putting an end to war."
Another research of 2011 confirmed: Given the growth in global population and the decline in armed conflict, it seems probable that a smaller proportion of humanity is directly affected by warfare today than at any time in human history. In our days, more people are killed by weather than in warfare. In 2010, more people died in Haiti's earthquake than in all the world's wars put together.
In 2012, the European Union was awarded the Nobel Peace Prize "for over six decades [having] contributed to the advancement of peace and reconciliation, democracy and human rights in Europe" by a unanimous decision of the Norwegian Nobel Committee. And another Nobel Peace Prize winner, Barack Obama, stated that even with all the turmoil in the world, this is a most peaceful era in history.
While there is general agreement among experts that we are in a Long Peace and that wars have declined since 1945, Pinker's broader thesis has been contested. Critics have also said that a longer period of relative peace is needed to be certain, or they have emphasized minor reversals in specific trends, such as the increase in battle deaths between 2011 and 2014 due to the Syrian Civil War. The prevailing popular view remains that the post-Cold War world is deadlier, less orderly, more dangerous and more turbulent.
Already in 1992, John Mueller noted that the pessimistic view survived the end of the Cold War and addressed the pessimists: Remember the "sword of Damocles?" Remember the "two scorpions in a bottle?" Remember the ticking doomsday clock on the cover of Bulletin of Atomic Scientist? (1992: 69). Robert Kagan also stressed the post-Cold War collective sklerosis: "During the Cold War, world leaders spoke more often about the possibility of nuclear war than we may care to remember." Despite the nuclear threats of Vladimir Putin, the motifs of Armageddon and Apocalypse do not characterize our days as they did the Cold War, when World War III looked inevitable to many experts and preventive nuclear war was seriously considered in the highest US circles. For proponents of the decline-of-war thesis, the only puzzle is why the pessimistic view prevailes disregarding the evidence: "If, explains Joshua Goldberg, we turn off the screech of 'alarmist' news and overblown political rhetoric for a moment and look at hard evidence objectively, we find that … in fact the world is becoming more peaceful. For this shocking idea to sink in requires either a paradigm shift or at least a broken TV set." His best explanation for the Doomsday Clock of the traditionally panic-stricken Bulletin "would seem to be that the Bulletin needs alarmism to attract interest and donors."
Pinker's work has received wide publicity and the Decline-of-War thesis reached a worldwide audience, which mostly found it compelling. According to Robert Jervis, the trends involve an order of magnitude or more. The extent of the decline of war and other forms of violence, which is still viewed with surprise and sometimes skepticism by non-specialists, is relatively uncontroversial within the research community, and the main disagreements are over the causes of the decline.

## Causes

Major factors cited as reasons for the Long Peace have included the deterrence effect of nuclear weapons, the economic incentives towards cooperation caused by globalization and international trade, the worldwide increase in the number of democracies, the World Bank's efforts in reduction of poverty, and the effects of the empowerment of women and peacekeeping by the United Nations. However, no factor is a sufficient explanation on its own and so additional or combined factors are likely. Other proposed explanations have included the proliferation of the recognition of human rights, increasing education and quality of life, changes in the way that people view conflicts (such as the presumption that wars of aggression are unjustified), the success of non-violent action, and demographic factors such as the reduction in birthrates.
Overlooked in the scholarly research but prominent among the US policy circles, the Neoconservatives and some other Anglo - American scholars is Unipolarity and the application of the Hegemonic stability theory to the US Hegemony or Pax Americana. Donald Trump calls it "peace through strength." Robert Kagan noted that Pinker traces the beginning of Long Peace to 1945, "which just happens to be the birthdate of the American world order. The coincidence eludes him but it need not elude us." The year 1945 also coincides with the advent of nuclear age thus leaving the puzzle open whether we live in Pax Americana or Pax Atomica. But the US Primacists stress that the next global drop in war in 1991 is unrelated to any unconventional invention and coincides with the "unipolar moment" when the US loses its bipolar counterweight. Vice versa, according to the approach, if the US primacy is challenged, war comes back and "all the best" about other causes of peace--UN peacekeeping, economic interdependence and the spread of democracy--"are right out of the window."

## Macrohistoric view

Critics have said that a longer period of relative peace is needed to be certain that the Long Peace is not an aberration. Pinker, however, considers the Long Peace to be part of a macrohistoric trend that has continued since prehistory, and other experts have made similar arguments. Undoubtedly the Second World War was the deadliest event in human history in terms of number of lives lost. Using these terms in their Arc of War, Jack Levy and William Thompson depict the Long Peace as a sharp drop after a five-centuries inflection and the pinnacle of the five-millennia arc during World War II. Counted as percentage of global population however a different trend appears and challenges the view of World War II as the deadliest war.
Furthermore, by almost any indicator, the century preceding World Wars (1914-1945) was the most peaceful in modern era. Statistics of Deadly Quarrels combined the period of World Wars and the preceding century (1820 to 1945) and calculated that, contrary to the popular belief, the percentage of killed per world population declined in this period relatively to the earlier Modern Time. The contemporary increase in world population seems not to have been accompanied by a proportionate increase in the deaths from war, indicating that mankind became more peaceful in this period. Jack Levy, who preferred absolute numbers unrelated to population for his Arc of War, observed: In modern time, war fatalities per population have been generally declining, suggesting that the deadliness of war has not kept up with the increase in population.
On this basis, the common characterization of the twentieth century as the world's most violent century becomes questionable. World War II casualties made up a smaller fraction of the world population than several earlier conflicts. Looking at relative casualties of the combatants, it was not deadlier than the Peloponnesian War, Second Punic War, Mongol conquests, or Thirty Year War. Moreover, these pinnacles of deadliest historical wars only approach the prehistoric average in terms of fatalities per population. For this reason, Pinker supposes that "we live in the most peaceful era of our species existence" and the Long Peace is only acceleration in the millennia-old trend which originated in prehistory.