In the late 13th century, Palestine and Syria became the primary front against the fast-expanding Mongol Empire, whose army reached Palestine for the first time in 1260, beginning with the Mongol raids into Palestine under Nestorian Christian general Kitbuqa. Mongol leader Hulagu Khan sent a message to Louis IX of France that Jerusalem had been remitted to the Christians under the Franco-Mongol Alliance; however, shortly thereafter he had to return to Mongolia following the death of Mongke, leaving Kitbuqa and a reduced army. Kitbuqa then engaged with the Mamluks under Baibars in the pivotal Battle of Ain Jalut in the Jezreel Valley. The Mamluks' decisive victory in Palestine is seen as one of world history's most significant battles, establishing a high-water mark for the Mongol conquests. The Mongols were, however, able to engage into some further brief raids in 1300 under Ghazan and Mulay, reaching as far as Gaza. Jerusalem was held by the Mongols for four months (see Ninth Crusade).