U.S. General David Petraeus receives a flag during a change-of-command ceremony at the NATO-led International Security Assistance Force (ISAF) headquarters in Kabul July 4, 2010. The nine-year war in Afghanistan has reached a critical stage, Petraeus said on Sunday, as he formally took command of the 150,000-strong NATO-led force fighting a deadly Taliban insurgency. REUTERS/Ahmad Masood (AFGHANISTAN - Tags: MILITARY POLITICS)