The Indo-Pakistani War of 1965 was a culmination of skirmishes that took place between April 1965 and September 1965 between Pakistan and India. The conflict began following Pakistan's Operation Gibraltar, which was designed to infiltrate forces into Jammu and Kashmir to precipitate an insurgency against Indian rule. India retaliated by launching a full-scale military attack on West Pakistan. The seventeen-day war caused thousands of casualties on both sides and witnessed the largest engagement of armored vehicles and the largest tank battle since World War II. Hostilities between the two countries ended after a United Nations mandated ceasefire was declared following diplomatic intervention by the Soviet Union and the United States, and the subsequent issuance of the Tashkent Declaration.