SINCE the Cold War ended, no region has experienced more shocks or a more significant reorientation in US foreign policy than South Asia. The big shift was enabled by the demise of the Soviet Union and New Delhi’s turn away from Nehruvian economics to market-oriented entrepreneurship.

Then came the 1998 nuclear tests, the Kargil war and the 9/11 attacks on US soil, which served to clarify Washington’s repositioning. Two of these bell-ringers occurred during the second term of the Clinton administration, when the big shift gained traction. After the 9/11 attacks, the subsequent US military campaign in Afghanistan and the US-India civil nuclear deal during the Bush administration solidified and accentuated Washington’s reorientation.

The end of the Cold War allowed New Delhi and Washington to view each other in a new light, a necessary but insufficient cause for a re-wiring of this magnitude. More consequential were the decisions by prime minister Narasimha Rao and finance minister Manmohan Singh to launch their market reforms in the early 1990s.

With this opening, powerful US interests could be mobilised to support initiatives to improve bottom lines. The rise of China and a far more politically active Indian-American community clearly reinforced economic impulses to improve ties between Washington and New Delhi.

India’s nuclear-weapon programmes were a major impediment to improved ties with Washington. Until 1998, India was perpetually caught betwixt and between: it couldn’t join global nuclear compacts, but was reluctant to rock the boat. New Delhi’s default position was to champion nuclear disarmament while wishing to join the nuclear club.

The indefinite extension of the Nonproliferation Treaty in 1995 and the negotiation of the Comprehensive Test Ban Treaty a year later forced a long-delayed choice. A new, determined coalition government, led by the Bharatiya Janata Party, finally pulled the nuclear trigger. Pakistan followed suit, and Washington had to adapt to new realities.

India remained in limbo after the nuclear tests because it chose not to sign the Comprehensive Test Ban Treaty and couldn’t rewrite the Nonproliferation Treaty. Washington’s cold shoulder lasted until Pervez Musharraf’s dangerous misadventure in the heights above Kargil. Musharraf may have been seeking to exploit Pakistan’s newly overt nuclear capability as a shield while forcing Indian concessions on Kashmir. Instead, he created a significant opening for US-Indian rapprochement.

Desperate for a face-saving exit, Prime Minister Nawaz Sharif pleaded with President Bill Clinton to take a more direct interest by visiting the subcontinent. By the time he did so, Pakistan was once again under military rule. Clinton spent five days in India and five hours in Pakistan. He then hosted the Indian prime minister and his entourage at a huge gala on the White House lawn.

The reversal of Indian and Pakistani fortunes was in full swing, and about to be accentuated by the incoming Bush administration, which was looking for a counterweight to China.

The 9/11 attacks offered a short-term fillip to US-Pakistan relations in the form of a lifting of sanctions and the influx of military and economic aid. But US-Pakistan relations have foundered over Afghanistan, where interests merge at a level of generality that is repeatedly undercut by specifics. The familiar Pakistani story of betrayal now has a companion US narrative.

Washington’s reliance on drone attacks has mortgaged relations with Pakistan in order to salvage bad decisions in Afghanistan. At the same time, Rawalpindi’s investments in the Afghan Taliban and outfits to serve as its strategic reserves against India have badly frayed ties with Washington.

These tactics have also accentuated Pakistan’s economic decline, domestic divisions and diplomatic isolation. Bilateral US-Pakistan relations can still be patched up, but not in meaningful ways as long as Rawalpindi’s policies mortgage Pakistan’s future, use the United States as a scapegoat and risk new confrontations with India.In contrast, US-Indian ties will improve, but in measured fashion. Familiar voices in the United States and India will continue to call on Washington to do more and to pick up the pace, even though New Delhi’s performance falls well short of expectations. It’s very hard for two proud and exceptional nations to forge a strategic partnership, especially given the viscosity of Indian bureaucratic and domestic politics. At the end of the day, New Delhi will refuse to be Washington’s junior partner.

After an eventful two decades, Pakistan feels jilted, while the romance of Washington’s new relationship with New Delhi has become routinised. The big shift in US foreign policy towards the subcontinent will not be reversed. But the upswing in US-India ties, like the downward trajectory of US ties with Pakistan, requires managed expectations.

The writer is the co-founder of the Stimson Centre in Washington.