A great game ecosystem, that never got enough attention. A publisher in France also made a variant based on the crusades that came with a comprehensive campaign mode. I liked those games, but they might feel slightly outdated now. One good thing about them : you had everything you needed to play in one box.
You can still get some of the Cry Havoc games of the Crusades and one for the Norman invasion. A few are still in print, some even with updated/thicker counters. I grabbed one from NobleKnight (US) not long ago since they've been regularly in stock there.
I had “Siege” many years ago it was a great game. The system is really good there were even rules to use miniatures with the game. They’ve actually produced new versions covering the adventures of Robin Hood in a game called “Sherwood” and a few other historical games. A UK shop called The Little Corporal sells them.