WASHINGTON - Four years after the U.S. invaded Afghanistan, Taliban and al Qaeda fighters are showing renewed strength, using suicide bombs and rocket-propelled grenades. They are even training the next generation. Since June 2005, 54 Americans have been killed in Afghanistan, by far the most lethal period since the U.S. invaded. Behind some of the most deadly attacks is one man, a 35-year-old Afghan who calls himself “Commander Ismail.” In his first interviews with Western media, Ismail brags about killing three Navy Seals this summer, then downing a Chinook helicopter that came to rescue them, killing another 16 Americans. Commander...