The guerrilla bands became known as the Black Hand ("al-kaff al-aswad"), an anti-Zionist and anti-British militant organisation. The idea for such a group appeared to have crystallised after the 1929 riots. From the outset, a split occurred in the movement. One faction led by Abu Ibrahim al-Kabir argued for immediate attacks against British and Jewish targets, while the other faction, headed by al-Qassam, thought than an armed revolt was premature and risked exposing the group's preparations. According to Subhi Yasin, a comrade of al-Qassam, the group's attacks in the north were executed by Abu Ibrahim's group in defiance of al-Qassam, though in 1969, Abu Ibrahim denied this allegation. The Black Hand's ensuing campaign began with the ambush and killing of three members of Kibbutz Yagur on 11 April 1931, a failed bomb attack on outlying Jewish homes in Haifa in early 1932, and several operations that killed or wounded four members of northern Jewish settlements. The campaign climaxed with the deaths of a Jewish father and son in Nahalal, from a bomb thrown into their home, on 22 December 1932.