WASHINGTON, May 13, 2010 – Afghan President Hamid Karzai, flanked by America’s top defense leaders, walked among the white marble tombstones at Arlington National Cemetery today, a silent tribute to U.S. servicemembers who made the ultimate sacrifice, many while battling terrorism in Afghanistan.Video Defense Secretary Robert M. Gates, right, Afghan President Hamid Karzai and John C. Metzler Jr., superintendent of Arlington National Cemetery, tour the cemetery's Section 60, in Arlington, Va., May 13, 2010. DoD photo by U.S. Navy Petty Officer 1st Class Chad J. McNeeley (Click photo for screen-resolution image);high-resolution image available. Defense Secretary Robert M. Gates; Navy Adm. Mike...