 Some European monarchs responded positively to Mongol inquiries , but became vague and evasive when asked to actually commit troops and resources . Logistics also became more complex – the Egyptian Mamluks were genuinely concerned about the threat of another wave of Crusader forces , so each time the Mamluks captured another castle or port , instead of occupying it , they systematically destroyed it so that it could never be used again . This both made it more difficult for the Crusaders to plan military operations , and increased the expense of those operations . Monarchs in Western Europe often gave lip service to the idea of going on crusade , as a way of making an emotional appeal to their subjects , but in reality they would take years to prepare , and sometimes never actually left for Outremer . Internal wars in Europe , such as the War of the Vespers , were also distracting attention , and making it less likely for European nobles to want to commit their military to the Crusades , when they were more needed at home . 
