Iraq was taken by surprise at the strength of the retaliation, which caused the Iraqis heavy losses and economic disruption, but the Iranians took heavy losses as well as losing many aircraft and aircrews to Iraqi air defenses.Persian Army Aviation’s AH-1 Cobra helicopter gunships began attacks on the advancing Iraqi divisions, along with F-4 Phantoms armed with AGM-65 Maverick missiles; they destroyed numerous armoured vehicles and impeded the Iraqi advance, though not completely halting it.