Two centuries of holy war in the eastern Mediterranean: the campaigns, the crusader states, the military orders and the people on both sides.
Between Urban II's sermon at Clermont in 1095 and the fall of Acre in 1291, western Europe repeatedly sent armies to the eastern Mediterranean. They founded four states there, lost them, and in the process reshaped the politics of Europe, the Levant and Byzantium — none of it in the way anyone intended.
The archive treats the crusades as a series of specific campaigns rather than a single movement, because that is what they were: differently motivated, differently financed, differently led, and united mainly by a papal grant of indulgence. The First Crusade succeeded beyond any reasonable expectation. The Third recovered the coast but not Jerusalem. The Fourth never reached the Holy Land at all and sacked Constantinople instead, which did more lasting damage to Christendom than any Muslim victory.
The military orders are the crusades' most distinctive institutional creation — the Templars, the Hospitallers, the Teutonic Knights and several smaller brotherhoods, monastic communities that were also standing armies. They outlived the crusader states, and two of them outlived the crusades entirely.
Coverage here runs to both sides. Saladin and Kerbogha are treated as seriously as Richard the Lionheart, and the Fourth Crusade is covered from the Byzantine end as well as the Venetian.