Protecting the United States from direct attack is the highest priority of the Department of Defense. The military has traditionally secured the United States by projecting power overseas. While our current missions abroad continue to play a vital role for the security of our Nation, the terrorist attacks of September 11, 2001, emphasized that we are confronting fundamentally different challenges from those faced during the Cold War. President George W. Bush activated all instruments of American power to respond to the attacks of September 11th, and directed the United States Government to better prepare for the reality of the 21st century threat. Working with Congress, President Bush established the Department of Homeland Security to prevent terrorist attacks in the United States. The Department of Defense, the traditional vanguard of America's security, began transforming as well. The stand-up of US Northern Command was an important first step - created to deter, prevent, and defeat aggression aimed at the United States. The Strategy for Homeland Defense and Civil Support marks the next significant milestone in reshaping the Department's approach to homeland defense. Building upon the concept of an active, layered defense outline in the National Defense Strategy, the Strategy for Homeland Defense and Civil Support constitutes the Department's vision for transforming homeland defense and civil support capabilities. It will fundamentally change the Department's approach to homeland defense in an historic and important way.