The Pakistan Air Force (PAF) launched a pre-emptive strike on Indian Air Force bases on 3 December 1971. The attack was modelled on the Israeli Air Force's Operation Focus during the Six-Day War, and intended to neutralise the Indian Air Force planes on the ground. The strike was seen by India as an open act of unprovoked aggression, which marked the official start of the Indo-Pakistani War. As a response to the attack, both India and Pakistan formally acknowledged the "existence of a state of war between the two countries" even though neither government had formally issued a declaration of war.