India's official entry into war on 3 December 1971

By December, it became apparent to Islamabad that it was not regaining control of East Pakistan. The muktijuddhas were striking deeply into East Pakistan in greater strength, and with border tension intensifying with India, the war took a decisive turn in favour of the muktijuddhas when Pakistan mounted a surprise attack on India.

Pakistani 'Operation Chengiz Khan' commences Indo-Pak war, lasting only 13 days

Indira Gandhi visited refugee camps in Kolkata on 3 December 1971, where she told a mass rally of Indian citizens and Bengali refugees gathered at the Brigade Parade Ground that India would "do what she considered to be in her national interest". Speaking in favour of the liberation struggle of Bangladesh and pledging all support and assistance to their cause, her speech was suddenly cut short. Yahya Khan, at 5.30pm, had opted for allout war against India.

Wary of the growing involvement of India and inflated by their support from the United States, China and the Gulf Arab states, the Pakistan Air Force (PAF) launched a pre-emptive strike on India on Sunday 3 December 1971. Code named 'Operation Chengiz Khan', Pakistan Air Force attacked eleven Indian airbases along the 1,400 miles border on the western front (separating India and Pakistan) on airfields in Punjab, Kashmir, Rajasthan and Uttar Pradesh.

By escalating the conflict Pakistan had hoped to rope in China and the US in widening the conflict and hoped for a UN intervention a la Kashmir. Their aim was to destroy as much Indian combat power as possible before she herself was attacked by India, and capture some territory which could be used to bargain for territory that was expected to be lost in the east. In opening up the western front to a full-scale war, Pakistan's military rulers were putting into practice their firmly held belief that the defence of East Pakistan lay in the west.

Yahya Khan sought to impose military means to resolve the mounting insurgency. Like the previous military dictator before him, President Ayub Khan, had once spoken of using "the language of weapons" if the "weapon of language" was unable to deal with a somewhat similar situation. Though Ayub had not lived long enough to see his phrase transformed into brutal fact, Yahya did.

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However, the plan failed to achieve the desired success. The Indian Air Force (IAF) had dispersed their aircraft to hardened shelters on a large number of airfields where only a direct hit could damage them. The late afternoon forced the attack to be brief as it could not be sustained in darkness. Not only were too few airfields struck for too short a time, but not every available aircraft were used - upto 50 planes were used. Indian runways were non-functional for several hours after the attack. The Pakistani action was not only unsuccessful but also seen as an open act of unprovoked aggression against the Indians.

The sudden attack took India by surprise. Whilst the Indian PM was in Kolkata, Defence Minister Jagjivan Ram was visiting his constituency in Bihar, Finance Minister Chavan was in Bombay, and President Giri was attending a reception on the lawns of Parliament House when an air alert was sounded at 5.45pm. When Indira Gandhi was informed in Kolkata, she flew at once to Delhi escorted by squadrons of air force fighter planes to ensure she not fall prey to Pakistani air strike in midair. Upon arrival in Delhi, she addressed the nation and declared war on Pakistan.

Today a war in Bangladesh has become a war on India... I have no doubt that by the united will of the people, the wanton and unprovoked aggression of Pakistan should be decisively and finally repelled... Aggression must be met and the people of India will meet it with fortitude, determination, discipline and utmost unity.

PM Indira Gandhi in a radio broadcast shortly before midnight on 3 December 1971

Following this, a full-scale, two-front war broke out between India and Pakistan - the third between India and Pakistan during their first quarter century of independence and the first that did not take place over Kashmir. New Delhi declared a state of national emergency, and the Indian Parliament passed the Defence of India Act giving emergency powers to the government. India also imposed an air and naval blockade of both East and West Pakistan, and publicly threw its support behind the Mukti Bahini.

Indian Air Force hit back hours after the Pakistan attack. Up until now there was limited use of Indian Army in Bangladesh cause, now it was used in full force. Indira Gandhi ordered the immediate mobilisation of troops and launched the full-scale invasion of Bangladesh in aid of the Mukti Bahini. This marked the official start of the Indo-Pakistani War of 1971 and would last until Pakistan Army surrendered in Bangladesh on 16 December 1971. Lasting just 13 days it's considered one of the shortest wars in history.

India was far superior to Pakistan militarily and played its hand cleverly. In particular, India had a larger, better-armed army and superior naval forces. It also had the advantage of being able to attack Pakistan on both its eastern and western fronts. Indian forces responded to Pakistani attack with a coordinated and massive air, sea, and land assault on East Pakistan.

Indian Army divided into three corps ready for action

In order to carry out their offensive, the Indian Army divided Bangladesh into three fronts - eastern, south-western and north-western - and split their ground forces accordingly. The capture of the eastern front was to be carried out by IV (or 4th) Corps commanded by General Sagat Singh. The south-western front by the newly raised II (2nd) Corps commanded by Lt. General T. N. Raina, and the north-western front by XXXIII (33) Corps commanded by Lt. General M. L. Thapan. With these Indian forces were the three Mukti Bahini brigades and sector troops numbering in their dozens of thousands.

The main thrust was to be delivered by IV Corps under Sagat Singh. He was tasked with launching an offensive to destroy the Pakistani forces deployed east of the Meghna Nodi. This included capturing Sylhet in the north, Comilla to the east, and intercepting surface communications, including road, rail and waterways, between Chittagong and the main hinterland and to the north. This operation may have also been called 'Operation Jackpot', similar to the famous naval attacks on August.

The eastern area was also the only area in which all three wings - army, navy and air force - of both the combatants took part in the military operations. As such this was the strongest of all the Mitro Bahini army corps. The main road and rail link of Dhaka with the important port of Chittagong passes through this area. The strategic bridge on the Meghna lies in this sector and so are the river ports of Chandpur and Daudkandi, located nearby. This entire area was a protecting shield for Dhaka.

The basic strategy for the war in 1971 was an offensive in the eastern wing of Pakistan and a defensive in the western wing.

Bengali 'Kilo Flight' commences air attack

The first 'Indian' air attack was actually carried out by Bengali air force of Kilo Flight. They launched successful air attacks on depots and communication lines on 2 December 1971 (i.e. the day before Pakistan attacked India). They then attacked a number of targets in Chittagong and Narayangonj in the early hours of 3 December 1971. The brave Bengali pilots destroyed the Jet Fuel Station at Chittagong and Godnail, Narayanganj and attacked the Mirpur Radar Station and Savar Radio Station and successfully destroyed it after the Mukti Bahini guerrillas had been unable to sabotage them due to the tight security. They flew the aircraft at an altitude of 40 to 250 feet so that enemy radars couldn't get the signal.

It must be remembered that this very fleet [i.e. new bangladesh airforce] struck first when all-out attack on the Pakistan forces began on 3 December 1971. We destroyed two fuel dumps - one at Godnail of Narayanganj and another in Chittagong - in that strike. It caused severe damage to the movement of the Pakistan army.

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Without any navigation equipment and proper air to air defense equipment, with obsolete planes, these people dared to fly and bomb Pakistani strategic position on 3rd December 1971. Their mission was to bomb 2 oil reservoirs, Godail and Chittagong. They flew from Kamalpur and bombed these two locations. This mission destroyed most of the reserve fuel of the Pakistani army.

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President Yahya: India's "aggression" leads to "point of no return"

On 4 December 1971 President Yahya addressed the nation where once again he blamed India's "aggression" for causing a situation which has led to "point of no return". He vowed to safeguard Pakistan's "territorial integrity" with all the forces in their command.

...India's hatred and animosity for Pakistan is world renowned. They have always attempted to weaken Pakistan and to destroy it...But this is the final straw. It's now time to give a solid response to the enemy. O' mujahid [one who engages in jihad] of Pakistan...rise and become a protective wall against this enemy. You are truthful and just...

Extract from President Yahya's radio speech on 4 December 1971

The radio in Islamabad proclaimed that Pakistan was waging a jihad against India. However, it became quickly clear that the Pakistani military had grossly overestimated its capabilities and the extent of the foreign support it might receive.

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Battle in the sky

These attacks were followed by several sorties against Pakistan by Indian Air Force (IAF), and within a week, IAF aircraft dominated the skies of East Pakistan. It achieved near-total air supremacy by the end of the first week as the entire Pakistani air contingent in the east, PAF No.14 Squadron, was grounded because of Indian airstrikes at Tejgaon (in Dhaka), Kurmitola (in Dhaka), Lal Munir Hat (Rangpur area) and Shamsher Nagar (below Moulvi Bazar, Sylhet Division). This enabled the advancing army columns to move without any fear of detection even in daytime.

For us in Dhaka, the war came in the form of strikes by the Indian Air Force over PAF base in Tejgaon in the midnight of 3 December. We could not sleep the whole night from the wailing sirens, the thunderous sounds of bombs that fell and the shrieking sound of the jets. We were excited that the war was finally there, but we were equally fearful that we could become victims of collateral damage. Fortunately, the accuracy of the bombing over targeted areas spared largely any civilian damage in Dhaka. Over next two-three days, we would witness thrilling low-level dog fights between PAF and IAF jets. The results of the IAF's assault were that by 7 December, the PAF in the East was effectively grounded.

Ziauddin M. Choudhury , author of "Fight for Bangladesh: Remembrances of 1971" (2011)

With supply from the air assured, the army did not have to be dependent on opening of roads, which were heavily defended by the Pakistanis. The five division-strong Indian forces advanced from three directions and secured choke points well in the rear.

Battle in the sea

Sea hawks from Indian navy ship INS Vikrant also struck Chittagong, Barisal and Cox's Bazar, destroying the eastern wing of the Pakistan Navy and effectively blockading the East Pakistan ports. This cut off reinforcements, supplies, and any escape routes for the stranded Pakistani soldiers. The Bangladesh Navy, which had only been formed four months back by defecting Bengali navy officers from Pakistan Navy, aided the Indians in the marine warfare.

Pakistan gave the first hint of surrender on 9 December 1971, within just six days of the joint attacks of the Indian armed forces and the Mukti Bahini began. Finally, they surrendered unconditionally on 16 December 1971.

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