U.S. Army Gen. David H. Petraeus, commander of U.S. and NATO forces in Afghanistan, addresses the Royal United Services Institute in London on Wednesday, March 23, 2011. Gen. Petraeus said foreign troops are on course to complete their security role in Afghanistan by the end of 2014, but he has warned that progress easily could be reversed. (AP Photo/Sang Tan)
Gen. David H. Petraeus (center) arrives on Capitol Hill on Wednesday to testify before the House Armed Service Committee. (Associated Press)
U.S. Army Gen. David H. Petraeus, commander of U.S. and NATO forces in Afghanistan, arrives on Capitol Hill in Washington on Tuesday, March 15, 2011, to testify before the Senate Armed Services Committee on the situation in Afghanistan. At left is Defense Under Secretary for Policy Michele Flournoy. (AP Photo)
U.S. Army Gen. David H. Petraeus, commander of U.S. and NATO forces in Afghanistan, testifies Tuesday on Capitol Hill before the Senate Armed Services Committee. (Associated Press)
Defense Secretary Robert M. Gates (right) talks with U.S. Army Gen. David H. Petraeus upon the Pentagon chief's arrival in Kabul, Afghanistan, on Monday, March 7, 2011. (AP Photo/Defense Department/Cherie Cullen)
"The sheer losses that they've sustained are tremendous. That in and of itself is very significant, and it's caused enormous stress on the central nervous system of the command and control structure," Army Gen. David H. Petraeus said. (Associated Press)
Vice President Joseph R. Biden Jr. (right) speaks with Gen. David H. Petraeus, the top U.S. and NATO commander in Afghanistan, during a press event in Kabul, Afghanistan, on Monday, Jan. 10, 2011. Mr. Biden is in Afghanistan on a surprise visit to assess progress in handing over security from foreign to Afghan forces. (AP Photo/Musadeq Sadeq)
Helmand's Gov. Gulab Mangal, left, shakes hand with U.S. Gen. David Petraeus, NATO's top commander in Afghanistan, in Lashkar Gah, Helmand province, south of Kabul, Afghanistan, Monday, Jan. 10, 2011. (AP Photo/Heidi Vogt)
President Barack Obama, followed by, from second from left, Gen. David Petraeus, Defense Secretary Robert Gates, Vice President Joe Biden, and Joint Chiefs Chairman Adm. Michael Mullen, walks to the Rose Garden of the White House in Washington, Wednesday, June 23, 2010, to announce that Petraeus would replace Gen. Stanley McChrystal. (AP Photo/Charles Dharapak)
