The United States can not win militarily in Afghanistan.
Pakistan regulates the operational tempo through its support of the Taliban and the Haqqani network as well as controlling the supply of our troops to landlocked Afghanistan.
Pakistan will always do just enough to prevent the U.S. from achieving its goals in the region unless there is a change in the strategic conditions that provides incentives to do otherwise.
There are three main elements to Pakistan’s foreign policy: Islamic extremism, nuclear weapons and a close alliance with China.
In addition to the use of the Taliban and the Haqqani network against Afghanistan, attacks are launched against India by Pakistan-based groups such as Lashkar-e-Taiba and against Iran by Jaish-al-Adl, virulently anti-Shia jihadis operating from safe havens in Pakistan.