The US officer who has done the most to build up ties with the Pakistan military has criticised it openly.
Adm Mike Mullen, the top US military official, has visited Pakistan more than 20 times, and invested an unusually large amount of time to build a relationship with Pakistan's army chief Gen Ashfaq Kayani.
Gen Kayani has invested an equal amount of time and energy in maintaining a close relationship with the US military, despite differences ever since the Afghan Taliban were defeated in 2001.
From the start, the Pakistan army objected to the occupation of Kabul by the Afghan Northern Alliance, the initial domination of the government by non-Pashtuns, and the refusal of the Americans to involve Pakistan in helping rebuild the Afghan army.
More differences arose after Pakistan gave sanctuary and support to the leadership of the Afghan Taliban who relaunched their insurgency in Afghanistan in 2003.
Since then the Taliban insurgency has grown to cover all of Afghanistan.
The US-Nato alliance has had to deploy 150,000 troops and the war has spawned the Pakistani Taliban, which the Pakistani army did not initially see as a danger but now sees as a major threat.
Yet throughout this time, as the relationship has changed, shaped by events on the ground and in Washington, the two men have remained close friends and have tried to understand the reasons for the strategy adopted by the other.
Each one has had to defend their relationship among their colleagues. Adm Mullen has been criticised by Congressmen, the CIA and even his military colleagues for being too soft on the Pakistan army.
