Although Iraq hoped to take advantage of Iran's post-revolutionary chaos and expected a decisive victory in the face of a severely weakened Iran, the Iraqi military only made progress for three months, and by December 1980 the invasion had stalled. As fierce fighting broke out between the two sides, the Iranian military started to gain momentum against the Iraqis and regained virtually all lost territory by June 1982, pushing the Iraqis back to the pre-war border lines. Following this, the next five years saw Iran go on the offensive until Iraq took back the initiative in mid-1988, and whose major offensives led to the final conclusion of the war. There were a number of proxy forces operating for both countries—most notably the People's Mujahedin of Iran, which had sided with Iraq and the Iraqi Kurdish militias of the KDP and PUK, which had sided with Iran. The United States, United Kingdom, Soviet Union, France, and most Arab countries provided an abundance of financial, political and logistical support for Iraq, while Iran was largely isolated.