In 1790, the First Congress of the United States established a small maritime law enforcement component within the Treasury Department to assist in collecting the new Nation's customs duties. For the next eight years, this Revenue Marine (later called the Revenue Cutter Service) was the Nation's only naval force and was soon assigned military duties. Over time, the Revenue Cutter Service merged with or absorbed other federal agencies. The Service acquired new responsibilities based upon its ability to perform them with existing assets and minimal disruption to its other duties. In some cases, the Service absorbed other agencies because their maritime responsibilities were seen as intersecting with or complementing its own. The result is today's U.S. Coast Guard-a unique force that carries out an array of civil and military responsibilities touching every facet of the maritime environment of the United States. The Coast Guard's distinct blend of authorities, capabilities, competencies, and partnerships provide the President, Secretary of Homeland Security, Secretary of Defense, and other national leaders with the capabilities to lead or support a range of operations to ensure safety, security, and stewardship in the maritime domain. The interrelated nature of the Coast Guard's missions and culture of adaptability provides the Service with the ability to rapidly shift from one mission to another as national priorities demand. The true value of the Coast Guard to the Nation is not in its ability to perform any single mission, but Publication 1 (Pub 1) explains who we are and what we do. It describes the fundamental roles and forces of today's Coast Guard. In keeping with our military nature, Pub 1 is consistent with Joint Publication 1 (JP 1), which is the capstone doctrine for unified action by the Armed Forces of the United States. It also aligns with Naval Doctrine Publication 1 (NDP 1), which describes how the U.S. Naval Services operate as an integrated force across a range of military operations. However, while we are a military service and a branch of the Armed Forces of the United States at all times, defense readiness is only one of the Coast Guard's missions. Pub 1 describes the full spectrum of our Service responsibilities. This document traces our history to explain how the Coast Guard acquired its diverse mission set. It explains the unique characteristics and qualities-derived from our history, roles, and missions-that collectively define who we are. Finally, it lays out principles of operations that flow from our particular organizational nature and identity. In other words, it also describes how we do things. The principles of operations discussed in this publication are Coast Guard doctrine; rooted in our history and distilled from hard won experience, they are fundamental concepts that guide our actions in support of the Nation's objectives. They provide a shared interpretation of the past and a common starting point for thinking about future directions. Together with training and experience, this shared outlook leads to disciplined action. Because this doctrine is rooted in history, it is enduring. But it also evolves in response to changes in the geo-political and strategic landscape, lessons from current operations, and the introduction of new technologies. Doctrine influences the way policy and plans are developed, forces are organized, trained and employed, and equipment is procured and maintained. It promotes unity of purpose, guides professional judgment, and enables Coast Guard active duty, reserve, civilian, and auxiliary men and women to best fulfill their responsibilities. Pub 1 tells us how we became-and why we are-the United States Coast Guard.