During the Iran–Iraq War, Iran made heavy use of its US-bought equipment, and lost at least eight CH-47s during the 1980–1988 period, most notably during a clash on 15 July 1983, when an Iraqi Mirage F1 destroyed three Iranian Chinooks transporting troops to the front line, and on 25–26 February 1984, when Iraqi MiG-21 fighters shot down two examples. On 22 March 1982, in Operation "Undeniable Victory", a key operation of the war, Iranian Chinooks were landed behind Iraqi lines, deployed troops that silenced their artillery, and captured an Iraqi headquarters; the attack took the Iraqi forces by surprise.