ROLE OF WORLD POWERS

USA

With full support to Pakistan in the 1971 war both politically and logistically, USA needed Pakistan to stop Soviet expansion into south Asia and also the Soviet alliance with India. President Nixon feared that Indian invasion of West Pakistan would mean Soviet domination of region and undermine the position of United States. USA encouraged Jordan and Iran to support Pakistan in this conflict with F-86, F-104 and F-5 fighter jets. The Nixon administration ignored the genocides in East Pakistan prompting a condemnation by the International Press. US ambassador to United Nations George HW Bush called for a ceasefire and withdrawal of armed forces by India and Pakistan and there was a huge pressure on the Soviets from Nixon-Kissinger duo to get India to withdraw but to no avail.
Before the imminent defeat of East Pakistani army, USA deployed, Task Force 74 led by the aircraft carrier USS Enterprise into the Bay Of Bengal.
Task Force 74: A Navy task force of the United States Seventh Fleet deployed into Bay of Bengal in December, 1971.
At the same time UAE sent in half a squadron of fighter aircraft and the Indonesians dispatched at least one naval vessel to fight alongside the Pakistani Navy.
Pakistan also had support from France and Turkey.
Pakistan already belonged to American led military Pact, CENTO and SEATO

When on April 28 1971, Kissinger sent a note defining the future policy option towards Pakistan, Nixon replied in a handwritten note: ‘Don’t squeeze Yahya at this time.’ The Pakistan president was not to be squeezed because he was in the process of arranging Kissinger’s first secret meeting to China. The events of the following months and the US position should be seen in this perspective. In May, Indira Gandhi wrote to Nixon about the ‘carnage in East Bengal’ and the flood of refugees burdening India.

After L K Jha, then the Indian ambassador to US, had warned Kissinger that India might have to send back some of the refugees as guerillas, Nixon commented, ‘By God we will cut off economic aid (to India).’
It was conveyed to Huang Hua, China’s envoy to the United Nations at the time that US would be prepared for a military confrontation with the Soviet Union if the Soviet Union attacked China.

China

People’s Republic of China reacted with alarm to the evolving situation in East Pakistan and the prospect of India invading West Pakistan and Pakistani-controlled Kashmir. The Nixon administration encouraged China to mobilise its armed forces along its border with India to discourage it. But the Indian Army had already deployed eight mountain divisions to the Sino-Indian border against any such eventuality. The Chinese did not proceed with the suggestions from Nixon administration. China was also among the last countries to recognise independent Bangladesh, refusing to do so until 31 August 1975.
The pact with Soviet Union was a shock for Washington as they saw a deliberate collusion between Delhi and Moscow. The Pakistani army kept on believing that China will open the Northern front which will slow down or completely stop the Indian advancement.

Lieutenant General A A K Niazi, the Pakistani army commander in Dhaka, was informed: “NEFA front has been activated by Chinese, although the Indians, for obvious reasons, have not announced it.” But in reality Beijing never took any such step.
The Tibetan Involvement -After the debacle of 1962, the Government of India had recruited some Tibetans youth in the eventuality of another conflict with China. The Special Frontier Force was trained in Chakrata in Uttar Pradesh under the command of an Indian general.

In 1971, nine years after its creation, the SFF was sent to East Pakistan to prepare for the arrival of regular Indian troops. Their saga is one of the least known parts of the Bangladesh war.
Source: https://en.wikipedia.org/wiki/Indo-Pakistani_War_of_1971
http://timesofindia.indiatimes.com/india/US-forces-had-orders-to-target-Indian-Army-in-1971/articleshow/10625404.cms
http://www.rediff.com/news/2006/dec/26claude.htm

United Kingdom

The United Kingdom deployed a carrier battle group led by the aircraft carrier HMS Eagle to the Bay, on her final deployment.
The Soviet Intelligence has reported that the English operative connection has come nearer to territorial India, water led by an aircraft carrier “Eagle” [On December 10].
For helping friendly India, Soviet government has directed a group of ships under the command of Admiral V. Kruglyakov. Vladimir Kruglyakov, the former (1970-1975) Commander of the 10th Operative Battle Group (Pacific Fleet) remembers: “But Soviet Union didn’t have enough force to resist if they encountered the British Carrier.

Therefore, to support the existing Soviet fleet in the Bay of Bengal, Soviet cruisers, destroyers and nuclear submarines, equipped with anti ship missiles, were sent from Vladivostok. In reaction English Navy retreated and went South to Madagascar.”

The commander of the Carrier Battle Group was then the counter-admiral Dimon Gordon. He sent the report to the 7th American Fleet Commander: ‘Sir, we are too late. There are Russian nuclear submarines here, and a big collection of battleships’.

1971 India Pakistan War: Role of Russia, China, America and Britain

Russia (Then Soviet Union)

The Soviet Navy dispatched two groups of cruisers and destroyers and a submarine armed with nuclear missiles from Vladivostok. They tracked US Task Force 74 into the Indian Ocean from 18 December 1971 until 7 January 1972.

The Soviets also had a nuclear submarine to help ward off the threat posed by USS Enterprise task force in the Indian Ocean. The Soviets were also instrumental in driving off the HMS Eagle from Bay of Bengal with a their threat of a huge arsenal of cruisers and destroyers.

Sri Lanka

Sri Lanka provided logistical support with the opening of its refueling facilities for Pakistani Aircrafts. The Pakistani Aircrafts flew via Sri Lanka as they could fly over Indian skies. Sri Lanka allowed Pakistani aircrafts for refueling at the Bandaranaike airport.

1971 India Pakistan War: Role of Russia, China, America and Britain