This is from the first hand account of De Vienne, the leader of the french expedition to Scotland in 1385. I read it in The Hundred Years War, volume 3, by Jonathan Sumption, around p500-600. The French expedition noted the abject poverty of the kingdom, the scarcity of men-at-arms, and the miserly nature of the scottish, who expected to be paid by the French for helping them in their war, as well as forced the French to pay for all of their supplies and for lodging and who would stop the French if they rode over a field in anything but single file. The French noted that the vast majority of scottish forces were light cavalry or infantry, who were more accustomed to looting than to fighting, and estimated that the scottish could produce no more than 500 properly equipped men-at-arms from their entire kingdom. This is merely 40 years before Verneuil. It is possible that the scottish could arm substantially more (with heavy French financial assistance) by 1424, but i think it incredibly unlikely that Scotland in total could put together more than 1500 men at arms even then, its far more likely that many of the rest of their numbers were made up of French, Breton and German mercenaries.
Yeah, I've read all of Sumption's work (twice). Might I suggest you take a look at the work of Dr Chris Brown, an actual Scottish Medieval Military historian. I don't have any of his books to hand so no quotes. I respect Sumption and have enjoyed reading his works, but he does have Anglophile tendencies (which obviously have to taken into account- national bias is normal in history of any description) as he does in his political outlook too (not sure if Lord Sumption is more famous/infamous for his jingoistic political commentary or his histories
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