Summary: In testimony before the Senate Armed Services Committee, Gen. David Petraeus, the U.S. commander in Afghanistan, says much of the Taliban’s battlefield momentum has been halted, putting the U.S. on course to begin pulling out troops in July 2011 and shifting security responsibility to the Afghans. He cautioned, however, that security progress remains “fragile and reversible,” with tough days ahead as the Taliban launch an expected spring offensive. … One-year retrospective: One year ago today, on March 15, 2010, Aubrey Immelman reported that the arrest of Mullah Abdul Ghani Baradar — second in the Taliban only to one-eyed leader Mullah Mohammed Omain — reportedly infuriated Afghan President Hamid Karzai, who was said to have been holding secret peace talks with the Taliban’s No. 2 when he was captured in Pakistan the previous month, in February 2010.