The Battle of Erkinholme was fought on the 1st of May, 1455.
The Battle of Erkinholme is more commonly referred to as the Battle of Arkinholm, albeit it's known by some as the Battle of Langholm, primarily because it was fought where the town of Langholm now stands. More accurately, the battle was fought on the outskirts of present day Langholm, opposite the lower return of a distinctive Z-shaped bend in the river Esk, which flows through the town, at least according to The Royal Commission on the Ancient and Historical Monuments and Constructions of Scotland. The battle is noteworthy for having pitched two sides of the Douglas family at each other's throats, but then again, that sort of thing wasn't so unusual in mediaeval Scotland or elsewhere, for that matter.
The two sides of Douglas were known as
the 'red' and the 'black'. The chief line as they say, of the Douglases was the 'black' line, represented by the Earls of Douglas, whereas the 'red' line was represented by the Earls of Angus. Both branches were descended through bastardy, with the Earl of Douglas descending from Archibald 'the Grim', an illegitimate son of Sir James Douglas, and the Earl of Angus stemming from an illegitimate child of William, the 1st Earl of Douglas. That made the main protagonists in the conflict at Erkinholme third cousins so, despite the name, the family ties weren't that close.
On the 'red' side was George Douglas, the first Red Chief of Douglas, the 4th Earl of Angus, Lord Douglas, Abernethy and Jedburgh Forest. Opposing his was James Douglas, the 9th Earl of Douglas, 3rd Earl of Avondale, a man who would become the last of the 'black' Earls of Douglas. Earlier in their history, in 1448, the two sides of Douglas, under the leadership of George and James' predecessor, the 8th Earl, had rode and fought together in a retaliatory campaign through the territories of their hereditary English-based foes, Percy and Neville. However, by 1455, things had changed dramatically.
A significant fact for Angus was his ties with the Royal House of Stewart, which were closer than that of his rival from the 'black' line. Through his grandmother, Angus was a great-grandson of Robert III and when push came to shove, he allied himself with his king, James II, also a cousin, but closer by a couple of degrees. George Douglas had no choice but to declare for one side or the other as neutrality wasn't an option for the Earl of Angus. Who knows what might have happened if the 4th Earl had aligned his Angus 'red' with the Douglas 'black'. Instead of a long line of Stewart (latterly Stuart) Jameses, we might've had an Archibald I or a William II and the entire interbred dynasty of European monarchies could have been otherwise than that we know.
A major incentive to rebellion for the 9th Earl of Douglas on the other hand, was the brutal murder of his brother, the 8th Earl, whom he succeeded because of that infamous event. Yet another 'black' day in Scotland's history had occurred when William Douglas had been murdered by his King, James II, in person, at Stirling Castle, despite assurances of safe conduct. Amazingly, James II was involved in the murders of two Douglas Earls. The first as a bystander during the 'Black Dinner' of the 24th of November, 1440, when the 6th Earl was killed, and the second as the primary perpetrator of the murder of William Douglas, on the 22nd of February, 1452.
When James Douglas found out he was the brand new 9th Earl, he denounced his brother's murderers and took up arms against the King and his cronies. The new Douglas Earl promptly attacked Stirling, perhaps rashly, but famously driving a horse through the town with his brother's safe conduct notice attached to its tail. The whole of Douglasdale rose in rebellion, but James suffered a blow when some major allies, including James Hamilton, 1st Lord Hamilton, defected. Nevertheless, he was supported by a bevy of surviving brothers: his twin (younger by a few minutes), Archibald Douglas, the Earl of Moray; the younger Hugh Douglas, Earl of Ormonde; and John Douglas, Lord of Balvenie.
James Douglas, the 9th Earl, didn't participate in person at the Battle of Arkinholm as he had gone south to drum up some support from Henry VI. His place at the head of the Black Douglases was taken by his twin, the Earl of Moray, with his brothers, Hugh and John. The Douglas Douglases attempted to advance their struggle and appeared in arms throughout their border territory, however, before they got as far as Langholm, they had already lost their castle at Abercorn. The writing was on the wall.
The ensuing Battle of Arkinholm was a small action, involving only a few hundred troops on either side, but it was a definitive defeat for the Black Douglas brothers. Archibald Douglas, the Earl of Moray, was killed in the battle and his head was presented to the King. Hugh Douglas, the Earl of Ormonde, was captured and executed shortly afterwards, but John Douglas, Lord of Balvenie, escaped to England, there to join the 9th Earl.
The Douglas Archive throws some doubt on whether or not the 4th Earl of Angus actually led the Royal Army as per some sources. The information on The Douglas Archive website refers to other accounts describing “a force of local Border families, Johnstones, Maxwells, and Scotts, who had previously been dominated by the Black Douglases, but now rebelled against them.” Those rebellious Douglas adherents were possibly led by the Laird John Johnstone of Johnstone in Annandale. Other accounts, less trustworthy, suggest that the King's supporters were led by Lord Maxwell.
Soon after Arkinholm, the last stronghold of the Black Douglas branch, Threave Castle in Galloway, fell to the King. Later, in the summer of 1455, the Black Douglases were attainted and had their estates declared forfeit to the crown. Following the acts of attainder, their lands were divided amongst their rivals, with Angus receiving the lion's share. Interestingly, the forfeited 9th Earl of Douglas outlived his erstwhile rival, the 4th Earl of Angus. James Douglas was captured a number of years after the Battle of Arkinholm and banished to Lindores Abbey, where he died in 1488. George Douglas died on the 12th of March, 1463, at Abernethy.