Relations between Washington and Islamabad deteriorated rapidly during 2011. A series of incidents, including the death of Osama bin Laden in an American raid in Pakistan and the killing of Pakistani soldiers by NATO forces in a skirmish on the Afghan border, created a poisonous atmosphere.
The causes of the deterioration were complex, bound up closely with divergent approaches towards the future of Afghanistan as the departure of Western combat forces approaches and towards the extremist groups which expect to play a part in that future. The situation was further complicated by the gulf between America's interlocutors in Pakistan: a dysfunctional civilian government barely tolerated by the military, which determines security policy. Cooperation with the military remains essential if Washington is to achieve its security objectives in the region.
Bilateral relations have never been easy. Since the 1950s the relationship has been characterised by on-off collaborations, each of which has involved both sides overlooking the degree to which their strategic objectives actually diverge. During each period of cooperation, the relationship has been able to defy gravity for a time. But sooner or later the laws of physics have re-asserted themselves and the relationship has come crashing to earth.