The United States and Pakistan have been close geopolitical allies almost since the birth of Pakistan in 1948. They have needed each other in the past. They need each other today. But their priorities and policy objectives have moved further and further apart. They are both appalled by the idea that the close alliance may end. But it may. 

The origin of the alliance was rather simple and straightforward. In the process of British withdrawal from India, two states came into existence, not one. Essentially, Pakistan broke away from India. Pakistan and India have been in steady conflict ever since. For each the greatest fear derives from the actions of the other. There have been three wars between the two – in 1947-48, in 1965, and in 1971. The first two were over Kashmir, the result of which was a de facto partition which neither side has ever accepted as legitimate. The third was over Bangladesh's secession from Pakistan, in which India sided with Bangladesh. 

One result of the continuing conflict was the refusal of both countries to sign the Nuclear Non-Proliferation Accord, and the development by each of nuclear weapons. India started first, probably in 1967. Pakistan followed, probably in 1972. By 1998, both had completed the process and had a stockpile of weapons. Nuclear weapons may have had the same positive effect on the two countries that they had on the United States and the Soviet Union – an undeclared superprudence about military hostilities, for fear of the consequences. 

India pursued from the outset a policy of non-alignment in the Cold War. The United States basically defined this policy as one tilting towards the Soviet Union. To limit the impact of this perceived tilt, the United States joined forces with Pakistan. While Pakistan hoped for U.S. support to recover the half of Kashmir it didn't control, what the United States wanted from Pakistan was its support for U.S. geopolitical control of the Moslem world to its west – Afghanistan, Iran, and the Arab world. The United States realized that the condition for this was internal stability in Pakistan. It therefore supported a succession of internally-repressive military regimes. It was not at all unhappy when the military deposed and then executed the one civilian leader, Zulfikar Ali Bhutto, who in the 1970s tried to pursue a nationalist foreign policy independent of U.S. control. 

Pakistan and the People's Republic of China were born in the same year. China too pursued a policy of close friendship with Pakistan. Its motives were not too different from that of the United States. China did not appreciate India's links with the Soviet Union, especially since it regarded (and still regards) India as a political and economic rival in Asia, one with whom they too had a war or "border conflict" in 1962. Nor has China appreciated the continuing support the Indian government has given the Dalai Lama. 

There were three things that began to upset the U.S.-Pakistan cozy arrangement in the last twenty years. The first was the collapse of the Soviet Union and therefore the end of the "cold war." This was combined with the end of the Nehru program of internal state-sponsored development and its replacement by a neo-liberal program inspired by the Washington Consensus. Suddenly, relations between India and the United States warmed up considerably, to the chagrin of Pakistan, and indeed of China. 

Secondly, the internal politics of neighboring Afghanistan changed as well. In the 1980s, Pakistan and the United States joined forces against the Soviet Union's military involvement in Afghanistan, which Gorbachev ended. But then what? It is no secret that the Pakistani intelligence service, the ISI, strongly backed the takeover by the Taliban of the Afghan government. But the Taliban regime offered its country as a convenient base for al-Qaeda, which the United States came to regard as its nemesis, even before al-Qaeda's successful attack of 9/11 on U.S. soil. 

Thirdly, with the overthrow of the Taliban in 2002 by a U.S.-led invasion, al-Qaeda forces retreated to secure bases in Pakistan. Al-Qaeda's program was, if not to take over directly the government of Pakistan, at least to force it to weaken, even break, its ties with the United States. Although Pakistan today has a civilian prime minister, real power still lies with the armed forces. And within the armed forces, the ISI still seems to play a very strong, perhaps determining, role. 

The cumulation of the three changes led to a situation in which, as of about 2005, the United States and Pakistan seemed to agree on very little of any importance. But the two countries seemed nonetheless to remain tied to each other, seemed to think that they still needed each other. Still, they became increasingly suspicious of each other's motives and actions. 

From the point of view of the U.S. government, Pakistan was the major source of outside support for the Afghan Taliban with whom the U.S. (and NATO) forces were in direct conflict. One part of this support came from the so-called Pakistan Taliban who were hard to distinguish from al-Qaeda. The second part of this support came from the ISI and perhaps from wider branches of Pakistan's military. 

It became increasingly obvious to the United States that the Pakistan military was neither willing nor able to contain the Pakistan Taliban/al-Qaeda forces. Worse, some of the Pakistan military may have colluded actively with them. The U.S. reaction was to intervene directly in Pakistan in two ways. The first was using its drones to attack directly targets they deemed dangerous. Of course, drones are notoriously hard to manipulate. There has been a great deal of "collateral damage," to the constant and repeated protest of the Pakistani government. The second way was to pursue on its own the finally successful search for Osama bin Laden, without informing the official Pakistani authorities, whom the United States clearly did not trust not to leak information about the intended attack. 

If the United States no longer trusts the Pakistani authorities, suspicion is even greater in the other direction. Pakistan has one great guarantee of its security – its nuclear weapons. As long as they have these, they feel defended against India and against anyone else. They believe, quite firmly, that the United States would like somehow to take possession of this stock. This is not entirely irrational, in that the United States does fear that al-Qaeda, or other hostile forces, might be able to get access to these weapons and that the Pakistani government may not be a position to stop this. Of course, such a putative U.S. attempt to take control of the stock is far from a practical proposition. But there are no doubt people in the U.S. government who do think about this. 

So now each side is playing its cards with each other. The United States is threatening to cut off, or drastically reduce, financial and military aid. The government is encouraged in this path by a U.S. Congress that is basically hostile to the alliance with Pakistan. Pakistan is retaliating by withdrawing the troops it had stationed on the Afghan border, making it easier than ever for the Pakistan Taliban to send military aid to the Afghan Taliban. Pakistan is also reminding the United States that it has another powerful ally, China. And China is quite happy to continue to support Pakistan. 

The weakness of Pakistan's regime is internal. Can it continue to control an increasingly anarchic situation? The weakness of the United States is that it doesn't have any real options in Pakistan. Playing it really tough with the Pakistani regime might undo its efforts to withdraw from Afghanistan (and Iraq and Libya) with minimal damage.