The four main crusader armies left Europe around the appointed time in August 1096. They took different paths to Constantinople and gathered outside its city walls between November 1096 and April 1097. The size of the entire crusader army is difficult to estimate. The princes arrived in Constantinople with little food and expected provisions and help from Alexios. Alexios was understandably suspicious after his experiences with the People's Crusade, and also because the knights included his old Norman enemy, Bohemond, who had invaded Byzantine territory on numerous occasions with his father, Robert Guiscard, and may have even attempted to organize an attack on Constantinople while encamped outside the city. The crusaders may have expected Alexios to become their leader, but he had no interest in joining them, and was mainly concerned with transporting them into Asia Minor as quickly as possible. In return for food and supplies, Alexios requested the leaders to swear fealty to him and promise to return to the Byzantine Empire any land recovered from the Turks. Before ensuring that the various armies were shuttled across the Bosporus, Alexios advised the leaders on how best to deal with the Seljuq armies that they would soon encounter.