On New Year's Day 1965, Fatah announced the formation of its military wing, called the al-Asifah forces, in Military Communique No. 1. This statement reported Asifah's first guerrilla attacks against Israel and officially declared the launch of the armed struggle for Palestinian independence. At the time, Fatah was far from ready for sustained military activity. Although al-Asifah was rooted in the organized guerrilla movements known as the Fedayeen, it had few trained volunteers and even fewer serviceable arms.
Its first attempted raid occurred on December 31, 1964, but was hindered when the fighters were detained by the Lebanese Armed Forces while planning to demolish a pumping station of the Israeli national water carrier. The following night a second al-Asifah unit infiltrated the border south of Lake Tiberius and laid explosive satchel in a water canal, which never detonated.In its early years, al-Asifah's direct military impact was negligible and their activities remained limited in scope and effectiveness. By the end of its first year, al-Asifah claimed to have carried out over 110 operations within Israeli territory. However, Israeli sources credit al-Asifah with a total of only 35 operations for the same time period.
Overall, al-Asifah only had limited success in spearheading an armed struggle against Israel. Its operations were more symbolic than effective, and their impact was more psychological than physical. Over time, the majority of al-Asifah forces were incorporated into the Palestinian Liberation Organization armed wing, the Palestinian Liberation Army. Although some units retained the name al-Asifah throughout the 1980s and 1990s, Fatah eventually re-branded its armed wing from al-Asifah to the Al-Aqsa Martyrs' Brigades following the outbreak of the Al-Aqsa Intifada in 2000.
Most Arab countries viewed al-Asifah's guerilla activities as reckless adventurism that could result in an untimely war with Israel. In 1965, the Lebanese Army Command requested that the Lebanese press stop publishing al-Asifah communiques and news of its operations. In January 1966, Arab representatives of the Mixed Armistice Commission demanded an end to activities by al-Asifah on the grounds that they were ineffective and causing Israeli reprisals. Measures to curb such incursions were agreed on. King Hussein of Jordan quietly but forcefully tried to prevent al-Asifah from operating in Jordanian territory. The first one of al-Asifah's men to die in action was killed by Jordanian border patrols while his unit was returning from a mission in Israel.
The only country to support the position of al-Asifah was Syria. The Baathist regime in power in 1966 had officially adopted the strategy of popular war of liberation as the only adequate method for achieving the liberation of Palestine. They offered to host al-Asifah's headquarters and allowed its members freedom of movement in Syria.