Too much has been written on this topic for me to contribute anything new.
During the 1950’s India & Communist Chinas were best of friends. I remember ‘Hindi Chinee bhai bhai’ slogan after signing of the 8 year Five Point agreement on peaceful coexistence in 1954. To the best my knowledge there was no border dispute between India & China before 1959. It was only Dalai Lama was given Asylum in India along with thousands of Tibetan refugees that India /China relations turned sour.
During the cold war era, US wanted to encircle the Communist block which then included China and was looking for client states. Pakistan could never match Indian Military machine quantitatively, hence her policy was to improve her military in quality this was done thru membership of Seato & Cento. Eisenhower administration built up Pakistan’s Army, Airforce & Navy ostensibly to fight the Communists. Nearly all the aircrafts & naval vessels until 1965 were acquired under the military assistance program, Pak Army got Patton tanks and artillery guns.
Re 1965 war, let us be clear, Pak military had been armed by the US as a bulwark against the Communist expansion, not to fight the Indians. Hence when 1965 war broke out US embargoed sale of spare parts & military hardware to Pakistan.
India with her greater financial resources had been able to increas her military capabilities multifold following the 1962 skirmish with China & 1965 war with Pakistan. By 1971 Indian armed forces, especially the Navy, were far stronger than Pakistan's. On the other hand Pakistan switched to Frances & China for the supply of military hardware but lack of financial resources prevented Pak Navy from modernization.
Nixon administration felt grateful to Pakistan for her facilitating the thawing of US/China relations and there was a clear tilt toward Pakistan. Hence, to forestall any untoward action by the US; in August 1971 Indra Gandhi signed a ‘Treaty of Friendship ‘with USSR before invading East Pakistan. By that time plight of Bengali refugees in India and their tales of Pak military atrocities had created unfavourable world opinion toward Pak military action.
Rightly or wrongly, I hold ZA Bhutto who had the slogan “Uther tum, ither hum” and precipitated the crisis by refusing to sit in the same parliament as Mujib ur Rahman partly responsible for 1971 debacle. ZAB’s culpability is also mentioned in the Humood ur Rahman report commissioned by Bhutto himself.
As far as US –Pakistan relations are concerned, in my humble opinion expectation from both the sides have been unrealistically high. It is unrealistic for US law makers to expect that Pakistan would toe the US line even if it goes against the Pakistan’s interest. Simultaneously to think the US would actively help in our fight with India was, is and would remain no more than wishful thinking.
Finally, age has taught me to be pragmatic. Not even China is going to help us liberate Kashmir; we would have to fight our own wars. We can blame the US all we want, but unless it is in her national interest, no country is going to help us during our war with India. Pakistan’s procrastination and not supporting Saudi Arabia in Yemen crisis proves my point.
