He was Senior Director for Proliferation Strategy, Counterproliferation and Homeland Defense within the National Security Council (2001–2005). In this capacity, he supervised the portion of President George W. Bush's 2003 State of the Union Address that dealt with intelligence on Iraqi weapons of mass destruction. Chairman Dianne Feinstein later proposed that her Senate Select Committee on Intelligence's probe of intelligence in the run up to the Iraq War question staff such as Joseph. In 2005 he succeeded John R. Bolton as Under Secretary of State for Arms Control and International Security.