So King Henry VIII of England decided he wanted his kid Eddie, who was, like, six years old at the time, to be promised the hand of little Mary, daughter of the Scottish king, in marriage. (She wasn't even two yet, so it's unlikely she was asked her opinion on the matter; dynastic politics are creepy as dammit.)
Now, if you wanted your son to marry your neighbor's daughter, what would you do? Well, if you were Henry VIII, you'd invade your neighbor's house and try burning it to the ground.
England went to war with Scotland in an attempt to fuse the dynasties in a conflict now called...in as British a manner as possible...the "Rough Wooing".
This conflict culminated in the English shooting up the Scots army at the Battle of Pinkie (I'm not making this up), a crushing English victory...only the Scots had already bundled Mary, now aged five, off to France and betrothed her to the Dauphin, which is what the French called the king's senior manchild. What a dolphin has to do with being a prince is one of those things that only monarchists understand, I guess.
Anyway, with the Scottish princess married off to the French prince of Viennois the odds got flip turned upside down and troopships began disgorging French soldiers and mercenaries from the Holy Roman Empire in Scottish harbors. It was obvious that, despite the shooting having tapered off with England holding a good-sized strip of southern Scotland, the Scots were willing to keep on fighting to the last Frenchman.
A peace treaty was concluded and, despite England having won on the battlefield, they went home without any territory or Scots princesses to show for their efforts.
.
