War engagements

by the end of April 1971, Prime Minister Indira Gandhi had asked the Indian Army chief General Sam Manekshaw if he was ready to go to war with Pakistan.According to Manekshaw's own personal account, he refused, citing the onset of monsoon season in East Pakistan and also the fact that the army tanks were being refitted. He offered his resignation, which Gandhi declined. He then said he could guarantee victory if she would allow him to prepare for the conflict on his terms, and set a date for it; Gandhi accepted his conditions. In reality, Gandhi was well aware of the difficulties of a hasty military action, but she needed to get the military's views to satisfy her hawkish colleagues and the public opinion, which were critical of India's restraint.

By November 1971, an Indian-Pakistani war seemed inevitable. The Soviet Union reportedly warned Pakistan against the war, which they termed as "suicidal course for Pakistan's unity. Despite this warning, in November 1971, thousands of people led by conservative Pakistani politicians marched in Lahore and across Pakistan, calling for Pakistan to "crush India". India responded by starting a massive buildup of the Indian Army on the western borders; the army waited until December, when the drier ground in the East made for easier operations and the Himalayan passes were closed by snow, preventing any Chinese intervention. On 23 November, President Yahya Khan declared a national state of emergency and told the country to prepare for war.

On the evening of 3 December, at about 17:40, the Pakistan Air Force (PAF) launched surprise pre-emptive strikes on eleven airfields in north-western India, including Agra, which was 480 kilometres (300 mi) from the border. At the time of the attack, the Taj Mahal had been camouflaged with a forest of twigs and leaves and draped with burlap, because its marble glowed like a white beacon in the moonlight.

These pre-emptive strikes, known as Operation Chengiz Khan, were inspired by the success of Israeli Operation Focus in the Arab–Israeli Six-Day War. Unlike the Israeli attack on Arab airbases in 1967, which involved a large number of Israeli planes, Pakistan flew no more than 50 planes to India.

In an address to the nation on radio that same evening, Prime Minister Gandhi held that the air strikes were a declaration of war against Indiaand the Indian Air Force (IAF) responded with initial air strikes the same night.These expanded to massive retaliatory air strikes the next morning.

This air action marked the official start of the Indo-Pakistani War of 1971; Gandhi ordered the immediate mobilisation of troops and launched a full-scale invasion of Pakistan. This involved Indian forces in massive coordinated air, sea and land assaults on Pakistan from all fronts.The main Indian objective on the Eastern front was to capture Dacca, and on the Western front was to prevent Pakistan from entering Indian soil. There was no Indian intention of conducting any major offensive into Pakistan to dismember it into different states.