The experiences of the U.S. Army in the Pacific provide significant insight into the complexity and uncertainty we face today. At a time when our Nation's leaders have called for a renewed emphasis on the Pacific, and many of our Soldiers have spent much of the last decade engaged in other parts of the world, it is important to review our long-standing engagement in this critical region. The Pacific has always played a significant role for the United States. Today, seven of ten of the largest armies in the world are in the Pacific and there are approximately 66,000 U.S. Soldiers stationed in the region. They are the modern day standard-bearers of an Army tradition dating back to 1803, when Lewis and Clark first gazed on the Pacific after leading the Corps of Discovery across the North American continent. In the future, this role will increase in significance as the Pacific becomes host to some of the world's largest populations, militaries, and economies. Whether it was the intense combat in World War II or disaster relief in northern Japan in 2011, the Army's experience in the Pacific is replete with lessons for the future. As this work clearly illustrates, the Army has conducted almost every conceivable mission in the Pacific region. From training Philippine forces in the 1920s to working as part of an international force in the 1930s, the Army learned and adapted to changes in the environment. Changes in national requirements caused the Army to transition from intense combat in Korea and Vietnam in the 1950s and 1960s to training and building partner capacity in Thailand and Japan in the 1990s. Simply put, the Pacific experience illustrates the breadth of missions the U.S. Army has conducted and provides a useful backdrop for those the Army must be prepared for in the future. The first chapter of this history describes the Army's forty-year engagement with the many diverse cultures, people, and languages of the Pacific. From these formative experiences rose Army leaders like Generals Marshall and MacArthur, who understood the complexity and interdependence of regions, cultures, and religions. In the future, as technology lowers barriers to communications and travel, building on a similarly well-developed understanding of the many dynamic factors present in this environment will be increasingly important. The Pacific also provides examples of joint, interagency, intergovernmental, and multinational operations. From the first time U.S. Army Soldiers sailed to the Philippines on Navy ships, through joint amphibious operations in the central Pacific, to multinational operations in the Korean Conflict and more recently, humanitarian relief operations in Japan, the Army has demonstrated the capability to operate in a joint, interagency, intergovernmental, and multinational environment. Soldiers and leaders can expect to build on these capabilities to provide the desired effects to achieve our Nation's objectives. Most importantly, this history is a timely reminder that change is the nature of the Army profession. The second and third chapters, dealing with World War II and the Cold War, relate the complex challenges the Army faced as former adversaries became partners and transnational terrorists threatened the world order. The Army's experience in the Pacific serves as a reminder that the only thing certain is the unexpected. Our Pacific history is one of both valor and strength, and provides the inspiration to secure our Nation's future.