Two of the fortresses the Order had acquired and strengthened were the castles of Margat and Krak in the County of Tripoli to the north of Jerusalem. Margat had been purchased in 1186 and its situation on the coast probably weighed the knights' decision to make it their new headquarters. Here they remained for a few years until some time after the recapture by Guy de Lusignan, King of Jerusalem, on 13 July 1191 of Acre, which then became the capital of the Christian kingdom. The Order moved their headquarters to Acre but continued to hold Margat and Krak until their final expulsion from the Holy Land in 1291.
Foster, Michael John: A Short History of the Order of St. John of Jerusalem, Part One. The Order of St John of Jerusalem until 1798
Sire, H.J.A.: The Knights of Malta, Yale University Press, New Haven & London, 1996 p.17