After the conquest of Jerusalem in 1099 during the First Crusade, the organisation became a military religious order under its own papal charter, charged with the care and defence of the Holy Land. Following the conquest of the Holy Land by Islamic forces, the knights operated from Rhodes, over which they were sovereign, and later from Malta, where they administered a vassal state under the Spanish viceroy of Sicily. The Hospitallers were one of the smallest groups to briefly colonise parts of the Americas: they acquired four Caribbean islands in the mid-17th century, which they turned over to France in the 1660s.