The international force finally captured Tianjin on 14 July. The international force suffered its heaviest casualties of the Boxer Rebellion in the Battle of Tianjin. With Tianjin as a base, the international force marched from Tianjin to Beijing, about 120 km, with 20,000 allied troops. On 4 August, there were approximately 70,000 Qing imperial troops and anywhere from 50,000 to 100,000 Boxers along the way. The allies only encountered minor resistance, fighting battles at Beicang and Yangcun. At Yangcun, the 14th Infantry Regiment of the U.S. and British troops led the assault. The weather was a major obstacle. Conditions were extremely humid with temperatures sometimes reaching . These high temperatures and insects plagued the Allies. Soldiers became dehydrated and horses died. Chinese villagers killed Allied troops who searched for wells.