For all practical purposes, the war started at about 5:40 pm on 3 December when Pakistan Air Force (PAF) combat aircraft struck nine Indian airfields along the Western borders. The air strikes were followed by a massive attack on the strategic Chhamb sector in the north. In the East, it was the Indian Army which went on the offensive. By late that night, artillery shells were raining down all along the Western and Eastern borders. India and Pakistan were locked in a two-front war.

Acting in accordance with its strategy to grab as much territory in the West as possible, Pakistan also launched a major attack on Punch in the state of Jammu & Kashmir. This attack, unlike the one on Chhamb, was completely repulsed, although here the Indian Army was at a locational disadvantage since the Pakistanis controlled the heights around the town. Smaller attacks were launched by Pakistan in Punjab at Fazilka and Hussainiwala. Here the forward Indian defences were breached but the Pakistani Army could not sustain its attacks. A more ambitious armoured thrust in the deserts of Rajasthan was similarly stopped in the famous Battle of Longewal. In all, it appeared that the Pakistani military high command could not make up its mind as to where it should deliver its main punch and kept pulling back until it was too late.

The Indian Army chief, General Sam Maneckshaw, had a completely different set of problems. His strategy had to take into account the Chinese, with whom the Indian Army had fought a full blown war only nine years earlier. The Chinese were now firm Pakistani allies and had been making threatening noises ever since India resolved to intervene in the East Pakistan issue. General Maneckshaw, despite the disappointment of his Corps and divisional commanders, had to hold back his Army in the West, keep a watchful eye on the long and difficult Chinese borders and, at the same time, ensure that his Eastern Army secured its objective of grabbing a good chunk of East Pakistani territory within 2 to 3 weeks. The Indian aim was to install a Bangladeshi interim government in East Pakistani territory before the cessation of hostilities.

The 4th morning saw Indian forces and Mukti Bahini guerrillas ready for battle with the Pakistanis, who were by now well dug in and waiting for the Indian assault. The Indian forces easily outnumbered the Pakistanis by a ratio of about 2:1. However, according to conventional infantry wisdom, an attacking Army requires a three-is-to-one superiority in numbers to attack. India did not have that. Besides, the Pakistani Army commander in the East, General A.A.K.Niazi, was determined merely to delay the Indian advance. For, in this war, the real battle was against time. The longer it took the Indian to secure their limited objectives, the greater the probability of the United Nations intervening to stop the war and effect a stalemate. Pakistan was confident that a stalemate was all that the Indians could get. Towards this strategy, General Niazi, had fortified the towns and approaches to the East Pakistani heartland and had boasted before the war began that should hostilities begin, he would take the battle inside India.

The brief given by the Indian Army chief, General Maneckshaw, to the Eastern Command was very limited. The aim was to occupy only two areas of East Pakistan - Chittagong and Khulna - so that an interim Bangladeshi government could be established. The capture of the whole of East Pakistan was not even conceived.

The immense practical problem of moving thousands of troops and tonnes of equipment across rivers and marshes was accomplished largely due to the efforts of the Army Corps of Engineers, and with a lot of local help. The IAF chipped in by using helicopters to lift entire battalions across larger rivers that could not be quickly bridged by the Engineers. In most places, the swiftly moving contingents quickly overcame enemy resistance and moved forward. The Pakistanis for the most part, were completely taken by surprise.Within 6 days of the war, Indian troops were deep inside East Pakistani territory and moving fast. The Mukti Bahini section of the advancing forces played a crucial role in guiding the Indian Army through the treacherous riverine areas and providing critical intelligence.

The 4th morning saw Indian forces and Mukti Bahini guerrillas ready for battle with the Pakistanis, who were by now well dug in and waiting for the Indian assault. The Indian forces easily outnumbered the Pakistanis by a ratio of about 2:1. However, according to conventional infantry wisdom, an attacking Army requires a three-is-to-one superiority in numbers to attack. India did not have that. Besides, the Pakistani Army commander in the East, General A.A.K.Niazi, was determined merely to delay the Indian advance. For, in this war, the real battle was against time. The longer it took the Indian to secure their limited objectives, the greater the probability of the United Nations intervening to stop the war and effect a stalemate. Pakistan was confident that a stalemate was all that the Indians could get. Towards this strategy, General Niazi, had fortified the towns and approaches to the East Pakistani heartland and had boasted before the war began that should hostilities begin, he would take the battle inside India.