 Despite the cooperation between the Mongols and their Christian subjects in Antioch , other Christians in the Levant regarded the Mongol approach with unease . Jacques Pantaléon , the Patriarch of Jerusalem , saw the Mongols as a clear threat , and had written to the Pope to warn him about them in 1256 . The Franks did , however , send the Dominican David of Ashby to the court of Hulagu in 1260 . In Sidon , Julian Grenier , Lord of Sidon and Beaufort , described by his contemporaries as irresponsible and light @-@ headed , took an opportunity to raid and plunder the area of the Beqaa Valley in Mongol territory . One of the Mongols killed was Kitbuqa 's nephew , and in retaliation , Kitbuqa raided the city of Sidon . These events added to the level of distrust between the Mongols and the Crusader forces , whose own center of power was now in the coastal city of Acre . 
