The Taliban's top military commander was captured in a secret joint operation by Pakistani and American intelligence forces in Pakistan. American officials have described the Afghan commander, Mullah Abdul Ghani Baradar, as the most significant Taliban figure to be detained since the American-led war in Afghanistan started more than eight years ago. Mullah Baradar has been in Pakistani custody for several days, with American and Pakistani intelligence officials both taking part in interrogations, according to the officials. The officials said his capture had provided a window into the Taliban and could lead to the capture of other senior officials. Most immediately, they hope he will provide the whereabouts of Mullah Omar, the one-eyed cleric who is the group’s spiritual leader.