American war became global in the 20th century, during World War II and the Cold War. War is one of the primary ways the United States relates to the world. I argue that the US foreign and military policy elite is captured by militarist beliefs. I discuss how the US became a continental power in the 19th century and how this set the US to become a global power in the next century. I then compare the 20th century globalization of U.S. war with the current era. Specifically, I explore how U.S. war and grand strategy have changed since 9/11 and what ways it is likely to change in the remainder of the 21st century. I argue that, in some ways, war and national security are now, more than ever, determining U.S. foreign policy and domestic politics. In this sense, while it is hyperbole to argue that war is no longer “politics by other means”, war, militarism, and the global reaction to these elements of U.S. behavior are the major factor determining the politics and foreign policy of the U.S. in the contemporary era. It is hard to see how war and politics are distinct spheres and because this situation has become normalized, there is a great deal of path dependency. This leads to the question of the consequence of this path for American hegemony, renaissance or decline over the next several decades.