This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Call something The Crusades and a reader pictures one thing: knights, Jerusalem, the eleventh century. The word actually covers nearly two hundred years of intermittent campaigns fought by different armies, for different popes, against different enemies, on three continents, and historians have never fully agreed on where to draw its edges.
The core is not in dispute. Pope Urban II stood at Clermont in November 1095 and called on Latin Christendom to march east and recover Jerusalem, promising the crusader's vow a plenary indulgence, full remission of the temporal punishment owed for sin, a spiritual reward with no real precedent. The First Crusade succeeded against long odds, taking Jerusalem in 1099 and carving out a set of crusader states along the eastern Mediterranean that would need defending, on and off, for two centuries.
Everything after that is where the edges blur. A Second and Third Crusade tried and largely failed to reverse Muslim reconquests. A Fourth Crusade, meant for Egypt, was diverted by debt and politics into the sack of Constantinople in 1204, a Christian city, and left a wound between the Latin and Orthodox churches that has never fully closed. By the time Acre, the last crusader foothold on the Levantine mainland, fell in 1291, the movement most people mean by The Crusades was over. But the machinery Urban II built, the indulgence, the vow, the papal call to holy war, did not retire with it. Popes turned it on the Cathars of southern France from 1209, on pagan peoples of the Baltic for two more centuries, and on Hussite Bohemia in the fifteenth century. Historians who study the movement as a whole, rather than only its most famous chapter, argue that the later, less remembered crusades are not a footnote to the real thing; they are evidence of what the real thing always was, a tool the papacy built once and reached for many times. This atlas keeps the narrower, Levantine timeline as the entry's own dates, and names the wider argument rather than resolving it, because it is not settled and should not be made to look settled.