The Second Crusade
The most disastrous of the crusades was the first, which ended, shockingly, in the sack of Jerusalem in 1099. The result would be the establishment of the Latin states of Outremer, constantly in need of defending, and a medieval cult of a “Greatest Generation” that later crusaders would be driven to emulate. In short: more crusading. The second crusade (in the normal way of reckoning these things) was a fiasco, its only real success (from the Christian point of view) being the by-the-way capture of Lisbon. Why they kept at it for another hundred and fifty years is hard to fathom today. It seems that one of the lessons of history is that no one learns from history.