For more than half a century, the United States has remained committed to helping the Republic of Korea (ROK, or South Korea) defend itself against external aggression. Modern South Korea is a far different country from the one that U.S. troops first entered at the beginning of the Cold War; it is now a strong democracy backed by the world’s eleventh largest economy and sixth largest military. The Cold War is over, but the threat that the Democratic People’s Republic of Korea (DPRK, or North Korea) poses to Northeast Asian peace and stability is not. The collapse of North Korea that many U.S. observers predicted has not occurred, and North Korean nuclear weapons and missile technology—in addition to its large conventional army and special operations forces—make North Korea more dangerous today than it was before. The realignment of U.S. forces in South Korea is recognition that the U.S. commitment to securing Northeast Asian peace, security and stability remains relevant today.Northeast Asia is of particular strategic importance to the United States as it is home to two U.S. allies and a rising China and contains a quarter of the world’s population and economic output. Among other consequences, instability on the Korean Peninsula could/would: seriously endanger the South Korean, Japanese and global economies; cause a conventional war with the United States and its allies as pyrrhic victors because of the hundreds of thousands of U.S. and South Korean deaths; increase the likelihood of regional nuclear and missile proliferation; precipitate a North Korean nuclear attack; and/or threaten the stability of the greater Asian region, including that of another important U.S. ally, Taiwan.This National Security Watch discusses the U.S. role on the Korean Peninsula and the future of Eighth U.S. Army in Korea. Although Japan, China and Russia should figure prominently in any discussion of Northeast Asia, this paper will focus mostly on North and South Korea; a forthcoming paper on the greater Asian security environment and U.S. Army Pacific will discuss these players in more detail.