It's time for some serious diplomacy. Secretary of State Hillary Clinton and Admiral Mike Mullen made a surprise trip to Pakistan aimed at calming tensions between the two countries following the mission against Osama bin Laden. Their meeting with President Asif Ali Zardari appeared strained, with little smiling and few opportunities for press. Clinton had been scheduled to visit Pakistan a month ago, but the trip was called off while the U.S. gauged Pakistan's reaction to the bin Laden raid. That reaction wasn't encouraging: They outed the CIA station chief and asked the Pentagon to remove its military advisers. This time, the visit was kept secret until the last moment and is scheduled to last no more than six hours. The State Department's Mike Grossman and the CIA's Mike Morrel went to Pakistan last week to prepare for Clinton's visit and to convince Pakistani intelligence to let the U.S. revisit the compound where bin Laden was killed, something they appear to have agreed to.