Question: Early Scandinavian Dublin, the First Viking Age in Ireland began in which year, when Vikings began carrying out hit-and-run raids on Gaelic Irish coastal settlements?

Context articles: Early Scandinavian Dublin
History of Ireland (800–1169)
Gaelic Ireland
Norse–Gaels
Viking raid warfare and tactics
Battle of Tara (Ireland)
Gofraid ua Ímair
Vikings
Longphort
Slavery in Ireland

The First Viking Age in Ireland began in 795, when Vikings began carrying out hit-and-run raids on Gaelic Irish coastal settlements.
 Over the following decades the raiding parties became bigger and better organized; inland settlements were targeted as well as coastal ones; and the raiders built naval encampments known as longphorts to allow them to remain in Ireland throughout the winter.
 In the mid 9th century, Viking leader Turgeis or "Thorgest" founded a stronghold at Dublin, plundered Leinster and Meath, and raided other parts of Ireland.
 He was killed by the High King, Máel Sechnaill mac Máele Ruanaid, which was followed by several Irish victories against the Vikings and the seizure of Dublin in 849.
 Shortly after, a new group of Vikings known as the Dubgaill ("dark foreigners") came to Ireland and clashed with the earlier Viking settlers, now called the Finngaill ("fair foreigners").
 The wavering fortunes of these three groups and their shifting alliances, together with the shortcomings of contemporary records and the inaccuracy of later accounts, make this period one of the most complicated and least understood in the fledgling city's history.
 In 853 a Viking warlord called Amlaíb (, possibly Olaf the White) arrived and made himself king of Dublin.
 He ruled along with his brothers Ímar ("Ívarr", possibly Ivar the Boneless) and Auisle ("Ásl").
 For the next fifteen years or so, they used Dublin as their base for a series of campaigns against Irish kingdoms.
 During these conflicts they briefly allied themselves with several Irish kings.
 The Dublin Vikings also carried out a number of raids in Britain at this time.
 The deaths of Ivar (c.873) and Olaf (c.874) were followed by internecine conflict among the Vikings.
 Although intermittent warfare between the Vikings and the Irish continued, these inner conflicts weakened the Viking colonies and made it easier for the Irish to unite against them.
 In 902, Cerball mac Muirecáin, king of Leinster, and Máel Findia mac Flannacáin, king of Brega, launched a two-pronged attack on Dublin and drove the Vikings from the city.
 However, in 914 the Vikings now known as the Uí Ímair (House of Ivar) would return to Ireland, marking the beginning of the Second Viking Age.
The history of Ireland 800–1169 covers the period in the history of Ireland from the first Viking raids to the Norman invasion.
 The first two centuries of this period are characterised by Viking raids and the subsequent Norse settlements along the coast.
 Viking ports were established at Dublin, Wexford, Waterford, Cork and Limerick, which became the first large towns in Ireland.
Gaelic Ireland (Irish: "Éire Ghaidhealach" ) was the Gaelic political and social order, and associated culture, that existed in Ireland from the prehistoric era until the early 17th century.
 Before the Norman invasion of 1169, Gaelic Ireland comprised the whole island.
 Thereafter, it comprised that part of the country not under foreign dominion at a given time.
 For most of its history, Gaelic Ireland was a 'patchwork' hierarchy of territories ruled by a hierarchy of kings or chiefs, who were elected through tanistry.
 Warfare between these territories was common.
 Occasionally, a powerful ruler was acknowledged as High King of Ireland.
 Society was made up of clans and, like the rest of Europe, was structured hierarchically according to class.
 Throughout this period, the economy was mainly pastoral and money generally not used.
 A Gaelic Irish style of dress, music, dance, sport, architecture, and art can be identified, with Irish art later merging with Anglo-Saxon styles to create Insular art.
The Norse–Gaels (Old Irish: "Gall-Goídil" , Irish: "Gall-Ghaedheil" or "Gall-Ghaeil ", Scottish Gaelic: "Gall-Ghàidheil" , "foreigner Gaels") were a people of mixed Gaelic and Norse ancestry and culture.
 They emerged in the Viking Age, when Vikings who settled in Ireland and in Scotland adopted Gaelic culture and intermarried with Gaels.
 The Norse–Gaels dominated much of the Irish Sea and Scottish Sea regions from the 9th to 12th centuries.
 They founded the Kingdom of the Isles (which included the Hebrides and the Isle of Man), the Kingdom of Dublin, the Lordship of Galloway (which is named after them), and ruled the Kingdom of York for a time.
 The most powerful Norse–Gaelic dynasty were the Uí Ímair or House of Ivar.
Vikings were members of tribes, originally from Scandinavia, of Norse ancestry, who gained a reputation for their raids and piracy in many parts of Europe, especially England, Ireland, and Frankish territories.
 The term "Viking Age" refers to the period roughly from 793 AD to the late 11th-century in Europe.
 In this era Viking activity started with raids on Christian lands in England and eventually expanded to mainland Europe, including parts of present-day Russia.
 While maritime battles were rare, Viking bands proved very successful in raiding coastal towns and monasteries due to their efficient ships, intimidating war-tactics, skilful hand-to-hand combat, and fearlessness.
 What started as Viking raids on small towns transformed into the establishment of important agricultural spaces and commercial trading-hubs across Europe through rudimentary colonization.
 Vikings' tactics in warfare gave them an enormous advantage in successfully raiding (and later colonizing) despite their small population in comparison to that of their enemies.
The Battle of Tara was fought between the Gaelic Irish of Meath, led by Máel Sechnaill mac Domnaill, and the Norse Vikings of Dublin, led by Amlaíb Cuarán.
 It took place near the Hill of Tara in Ireland in the year 980.
 The battle was a devastating defeat for the Vikings and led to the Irish regaining control of Dublin.
Gofraid ua Ímair (Old Norse: "Guðrøðr" , died 934) was a Viking leader who ruled Dublin and briefly Viking Northumbria in the early 10th century.
 He was a grandson of Ímar and a member of the Uí Ímair.
 Gofraid was most probably among those Vikings expelled from Dublin in 902, whereafter he helped his kinsman Ragnall conquer Northumbria.
 Another kinsman, Sitric Cáech, became ruler of Dublin around the same time.
 Ragnall died in 920, and so the following year Sitric left Dublin to rule in Northumbria, and Gofraid succeeded Sitric as ruler of Dublin.
 Sitric's early reign was marked by raids he conducted against the native Irish, including one at Armagh.
Vikings (Old English: "wicing"—"pirate", Danish and Bokmål: "vikinger" ; Swedish and Nynorsk: "vikingar" ; Icelandic: "víkingar" , from Old Norse "víkingar "), were Norse seafarers, mainly speaking the Old Norse language, who raided and traded from their Northern European homelands across wide areas of northern, central and eastern Europe, during the late 8th to late 11th centuries.
 The term is also commonly extended in modern English and other vernaculars to the inhabitants of Viking home communities during what has become known as the Viking Age.
 This period of Nordic military, mercantile and demographic expansion constitutes an important element in the early medieval history of Scandinavia, Estonia, the British Isles, France, Kievan Rus' and Sicily.
A longphort (Ir.
 plur.
 "longphuirt") is a term used in Ireland for a Viking ship enclosure or shore fortress.
 Although it can be assumed that the "longphorts" were used as bases for Viking raids, it is clear that the term had multiple meanings and that these sites had multiple purposes.
 The reason it cannot be assumed that "longphorts" were solely for military purposes as that would assume that there were always large numbers of Vikings at these settlements, which is not true.
 These camps were fortified areas along rivers, usually at a tributary where both sides were protected such that the Vikings could port ships.
 The sites were easily defended, sheltered, and gave immediate access to the sea.
 These camps would be of great importance to the Vikings during their raids of Ireland, which included attacks on many churches and monasteries located on the coast of Ireland.
 It can be assumed that the purpose of these sites was to ease travel and trade within the region.
 Longphorts were essential to the economic prosperity of the Vikings.
 For example, it is clear that the earliest settlements became major trading centers throughout Ireland.
 Archeological evidence shows that imports and exports included textiles, animal skins, amber, and glass from England.
 During this time, the Vikings were able to begin a period of extremely profitable trade.
 Overall, the longphort settlements were essential in establishing the presence of the Vikings in Ireland during the ninth and tenth centuries.
Slavery had already existed in Ireland for centuries by the time the Vikings began to establish their coastal settlements, but it was under the Norse-Gael Kingdom of Dublin that it reached its peak.
 Gaelic raiders kidnapped and enslaved people from across the Irish Sea for two centuries after the Fall of the Western Roman Empire destabilised Roman Britain; their most famous victim was Saint Patrick.
 The raids were discontinued after the British kingdoms consolidated, although an internal trade continued in enslaved prisoners of war and debt slaves caused by famine.