From the onset of the eleventh century, the world was a mass battlefield, and it was the castle that evolved into the mainstream method of fortification and defense. So easily constructed and so simply adequate, the castle came to signify the opening move in the real-world game of chess that prevailed in the later middle ages. Because castles were so adept at fending off attacks, and the high cost of both maintaining a field army and the repercussions of losing a massed army in battle, siege warfare eventually became so much the norm as to almost defunct open battle completely. In fact, ninety-nine percent of all warfare was sieges, and the one percent of battles normally developed from a siege (Bradbury 71).
Because castles tended to appear everywhere, and because they offered such good protection if utilized efficiently, the princes and castellans all in within their own territories developed a system of 'mini-kingdoms'--wherein they not only were keen to "defending their own districts, or rather plundering them" (Bradbury 76), in some cases they proved pivotal in the ever-changing world of allies and loyalty.
Although there challenge to immediate authority was sometimes beneficial--as some castellans emerged as uncontrollable tyrants, like antiquated mafia lords, there was however, the ever present danger of their loyalty falling short of a lord's grace during power struggles: "no man....can serve two masters" (Orderic Vitalis from Bradbury 77, footnote 27).
As in chess, the opening move representing a challenge to the opponent, so too was the meaning behind the siege--and thus, the game of challenge and withdrawal began. In fact, as far as siege warfare goes, "to challenge an opponent the most obvious ploy was to besiege one of his castles. It was a challenge to his lordship. If your opponent wished to retain power, he...