Relations between the United States and Pakistan have continued to fray since a U.S. Special Forces team killed Osama bin Laden in a comfortable villa near a major Pakistani military academy. But the tit-for-tat retaliations that have followed the raid reflect deeper sources of mistrust and mutual suspicion.

The latest round has focused on the alleged activities of the Pakistani military's powerful intelligence agency, Inter-Services Intelligence (ISI), in the United States. ISI is accused of watching over the Pakistani diaspora and of sponsoring unregistered lobbyists working to shape congressional opinion.

Indeed, this is not the first time that Pakistan's relations with the U.S. have been on a slippery slope. In 1965, after helping the country to build up its economy and its military strength, the U.S. walked out over the war with India that Pakistan had provoked by sending "freedom fighters" into Kashmir.