This book explores U.S. border security and the role of the key agencies and their missions. The U.S. Border Patrol (USBP) has a long and storied history as our nation's first line of defence against unauthorised migration. Today, the USBP's primary mission is to detect and prevent the entry of terrorists, weapons of mass destruction, and illegal aliens into the country, and to interdict drug smugglers and other criminals along the border. In the wake of the tragedy of September 11th 2001, the U.S. Congress decided that enhancing the security of the U.S. borders was a vitally important component of preventing future terrorist attacks. After the massive reorganisation of federal agencies precipitated by the creation of the Department of Homeland Security (DHS), there are now four main federal agencies charged with securing the U.S. borders: the Bureau of Customs and Border Protection (CBP), the Bureau of Immigrations and Customs Enforcement (ICE), the U.S. Coast Guard, and the Transportation Security Administration (TSA). This book serves as a primer on the key federal agencies charged with border security and describing each agency's role. This book consists of public documents which have been located, gathered, combined, reformatted, and enhanced with a subject index, selectively edited and bound to provide easy access.