The second Indo-Pakistani conflict (1965) was also fought over Kashmir and started without a formal declaration of war. It is widely accepted that the war began with the infiltration of Pakistani-controlled guerrillas into Indian Kashmir on about August 5, 1965. Skirmishes with Indian forces started as early as August 6 or 7, and the first major engagement between the regular armed forces of the two sides took place on August 14. The next day, Indian forces scored a major victory after a prolonged artillery barrage and captured three important mountain positions in the northern sector. Later in the month, the Pakistanis counterattacked, moving concentrations near Tithwal, Uri, and Punch. Their move, in turn, provoked a powerful Indian thrust into Azad Kashmir. Other Indian forces captured a number of strategic mountain positions and eventually took the key Haji Pir Pass, eight kilometers inside Pakistani territory.

The Indian gains led to a major Pakistani counterattack on September 1 in the southern sector, in Punjab, where Indian forces were caught unprepared and suffered heavy losses. The sheer strength of the Pakistani thrust, which was spearheaded by seventy tanks and two infantry brigades, led Indian commanders to call in air support. Pakistan retaliated on September 2 with its own air strikes in both Kashmir and Punjab. The war was at the point of stalemate when the UN Security Council unanimously passed a resolution on September 20 that called for a cease-fire. New Delhi accepted the cease-fire resolution on September 21 and Islamabad on September 22, and the war ended on September 23. The Indian side lost 3,000 while the Pakistani side suffered 3,800 battlefield deaths. The Soviet-brokered Tashkent Declaration was signed on January 10, 1966. It required that both sides withdraw by February 26, 1966, to positions held prior to August 5, 1965, and observe the cease-fire line agreed to on June 30, 1965.