Providing for the common defense was a crucial and basic government obligation that has been of importance since the Preamble of the Constitution. With the Revolution fresh in their minds, American leaders considered Britain the main enemy and a second war and possible invasion their greatest threats. France, although being a Revolution ally, claimed ownership of a huge tract to the west that posed a potential threat to American interests. In the interior of the United States, settlers confronted American Indians as the boundaries of the country pushed west. The Army and the Navy were the homeland defense. Fort Monroe, Va., Fort Washington, Md., and Fort McNair, Washington, D.C., are also remnants of these homeland defense efforts. While Americans still considered the Atlantic and Pacific oceans enough of a defense against foreign enemies, a strong Navy upon those waters was important.