Secretary Cohen responds to a question during a press briefing on NATO Operation Allied Force. Secretary of Defense William S. Cohen responds to a reporter's question during a Pentagon press briefing on NATO Operation Allied Force, on March 24, 1999. Cohen announced the U.S. participation in the NATO air operation against targets the Federal Republic of Yugoslavia. SHARE: Download: Full Size (0.03 MB) Credit: VIRIN: 137230-C-KLY82-276.jpg Photo Gallery