|Jarldom of the Five Boroughs|
|.' 'c. 1016 - Present|
|Map of the Five Boroughs (red) within England (light red), 1315|
|Official languages||Old Norse, English|
|-||Ascension of Cnut the Great||1011|
|-||Establishment of Jarldom||c. 1016|
|-||Crisis of the Boroughs||1087 - 1089|
The Jarldom of the Five Boroughs, also known as theBoroughs of the Danelaw in early English history, refers to the original five cities settled by the Danish in central Englandfollowing the War of the Great Heathen Army, independent of the major city of Jórvík in the north. Established as an official jarldom within the Kingdom of England in about 1016 byEnglish king Cnut the Great, the Jarldom of the Five Boroughs became one of England's most important regions during its early history, as a major concentration of the nation's Danish-English population.
In 1087 the Five Boroughs was the battlefield for the First Crisis of the Boroughs, an early English civil war instigated by the House of Hvitserk against English king Sweyn II's half-brother Jarl Alfvin I. After restoring order to the region, civil war again broke out in 1098, beginning the Second Crisis of the Boroughs. The crisis was paralleled by a war in East Anglia, nicknamed the Elmthorp War, which saw the usurping of the House of Knýtlinga by the House of Thetford. As part of the peace that ended the conflict in 1100, additional jarldoms were created to curtail the expansion of the Jarldom of Merica, such as the Jarldom of Gloiuborg, later a stronghold of the House of Hereford, and the Jarldom of Grantebrú several years later.
The Jarldom of the Five Boroughs would continue to be influential in English politics for years to come, being ruled by a cadet branch of the House of Hereford under Björn I, son ofUlf I of England. Björn's descendants would also rule over the Duchy of Brittany, until its conquest by the Plantagenets following the Twenty Years' War in 1213. During the War of the Axes the jarldom served a major part in the conflict due to its central location within England. The jarl Alfvin II would be responsible for the 'New Years' Massacre', which would claim the life of Ulf I of Jórvík and many of his supporters. During the later half of the conflict the Five Boroughs' rivalry with Mercia resulted in a partial occupation by the Tamworth Union, and the Five Boroughs was instrumental in leading the war effort to dissolve the separatist kingdom.