The most notable impact upon the Department of Defense (DOD), in creating the Department of Homeland Security (DHS), has occurred in how DOD prepares for and provides homeland defense and homeland security. Creating DHS produced friction for DOD resulting in re-focused training on domestic military missions and homeland security that has reduced combat effectiveness in some units. Resource allocation throughout DOD and DHS is an area of important concern regarding long-term sustainment in the war on terrorism. This study concludes that the current mission approach for DOD is not sustainable over the long term. Furthermore, greater fiscal responsibility in strategically funding homeland defense and homeland security needs to be exercised without compromising national security.