islamabad tie unite state pakistan veer extremes past four decades key moments turbulent relationship 1980s unite state pump weapons money foreign fighters afghanistan help pakistan inter-services intelligence isi spy agency support mujahideen fighters defeat soviet union troop afghanistan 1990 unite state impose sanction pakistan islamabad covert nuclear program soviet union rout afghanistan cold war end pakistan lose importance regional ally 1998 unite state impose sanction pakistan india nuclear test 1999 washington impose sanction pakistan army chief pervez musharraf topple democratically elect government military coup 2001 sept. 11 attack new york washington unite state ask musharraf help track al qaeda remove taliban power pakistan turn former taliban ally arrest al qaeda leaders washington remove sanction pakistan wake pakistan support war al qaeda islamist militant group afghanistan 2004 george w. bush administration designate pakistan major non-nato ally boost islamabad diplomatic prestige give pakistan great access u.s. military technology 2011 cia contractor raymond davis kill two pakistanis eastern city lahore january 2011. davis acquit murder allow leave pakistan 2.3 million payment make men families u.s. troop kill osama bin lade pakistani soil may 2011. raid keep secret pakistani authorities humiliation pakistan powerful military raise question whether harbor militants nato helicopters fighter jet attack pakistani military outposts accident kill 24 soldier pakistani retaliate block nato supply route territory afghanistan seven months 2016 u.s. congress block sale f-16 fighter jet pakistan military aid pakistan reduce 2017 u.s. president donald trump outline new south asia policy trump accuse pakistan harbor agents chaos provide safe havens militant group wag insurgency u.s.-backed government kabul factbox u.s.-pakistan tie falter afghanistan war drag