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While I'm thinking about 15th century English WIs... What if something goes right for the French at Agincourt? Maybe the rain holds off for a bit so that the ground's better for them; maybe that cavalry attack they'd planned on the flanks is a bit more coherent, with more manpower behind it, and they put a serious dent in the English archers. Maybe Henry V just has an uncharacteristically bad day at the office.​

Whatever happens, the dismounted French men-at-arms advancing through the mud and the arrows manage to land a telling blow. The English are pushed back; a push back becomes a rout, becomes a massacre. King Henry and his brother Humphrey duke of Gloucester are among the dead.​

So:​

The leadership of the French Armagnac faction is probably mostly intact, with a more-or-less intact army and maybe some high-status English prisoners. What next? They could try and take Harfleur back, or maybe march on Calais. Except...​

...Duke John the Fearless of Burgundy is in Dijon with an army of his own. In theory, Armagnacs and Burgundians have put their differences aside to jointly repel Henry V's invasion. In reality, John was waiting and seeing what happened before he made his move (in OTL he took advantage of the mostly-Armagnac defeat at Agincourt to march on Paris). What is he going to do now? Sit tight? Opportunistically go after Calais himself?​

Thomas duke of Clarence, the slain Henry's younger brother and heir presumptive, is in Calais. He is now King Thomas I of England. He went there from Harfleur rather than join the march that led to Agincourt, allegedly sick. In reality, it is suspected that he was got out of the way by Henry because of his opposition to the march and his close personal ties to leading Armagnacs like Charles d'Orleans and Charles d'Albret. Does the new king now try to salvage what is left of England's fortunes in France by arranging a truce with his Armagnac friends, maybe to help offset any Burgundian move against English possessions.​

Henry V was operating a pro-Burgundian diplomacy before he died. His next oldest brother, John duke of Bedford, was left in England as lieutenant while Henry was campaigning in France, governing with the aid of a council headed by the Archbishop of Canterbury. What does he do, especially if he trusts Thomas about as much as Henry did? Although, Thomas is now the king...​

(Hmm...might be more interesting to have Henry alive and in French captivity, so that Thomas and John can squabble over the best course of action in France and the dauphin's faction can demand a predictably massive ransom from England...)​

Oh, and if the vast majority of the English archers at Agincourt were killed either in or after the battle, that sort of trained manpower is hard to replace quickly. Yes, Henry had sent a lot of sick men back to England or Calais from Harfleur, so the massacre of the army at Agincourt would not mean the destruction of the entire force he had mustered from the French campaign (maybe only half of it). Still, it would be a blow to England's immediate term military outlook.​

So yes, thoughts, suggestions on where things would be likely to go from there?​
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