PLO and Lebanese weapons captured by the Israelis in their invasion of Lebanon in June 1982 were of Soviet origin and were then covertly transferred into Afghanistan through Pakistan. Later, when American support for the Mujahideen became obvious, Stinger Missiles and other high-technology American weaponry were transferred through Pakistan into Afghanistan. However some of these weapons may have been siphoned off by the ISI for reverse engineering purposes. The arrival of the new high-technology weaponry proved to be quite helpful in organising stiff resistance against the Soviet Union. Many Army regulars fought in Afghanistan along with the resistance and contributed to the withdrawal of Soviet forces from Afghanistan in 1989.