The Muslims set out for Khaybar in March 628, Muharram AH 7. According to different sources, the strength of the Muslim army varied from 1,400 to 1,800 men and between 100 and 200 horses. Some Muslim women (including Umm Salama) also joined the army, in order to take care of the wounded. Compared to the Khaybarian fighting strength of 10,000, the Muslim contingent was small, but this provided an advantage, allowing them to swiftly and quietly march to Khaybar (in only three days), catching the city by surprise. It also made Khaybar overconfident. As a result, the Jews failed to mount a centrally organized defense, leaving each family to defend its own fortified redoubt. This underestimation of the Muslims allowed Muhammad to conquer each fortress one by one with relative ease, claiming food, weapons, and land as he went.