The United States Department of Homeland Security (DHS) is the U.S. federal executive department responsible for public security, roughly comparable to the interior or home ministries of other countries. Its stated missions involve anti-terrorism, border security, immigration and customs, cyber security, and disaster prevention and management.
It began operations in 2003, formed as a result of the Homeland Security Act, enacted the previous year in response to the 9/11 attacks. With more than 240,000 employees, DHS is the third largest Cabinet department, after the Departments of Defense and Veterans Affairs. Homeland security policy is coordinated at the White House by the Homeland Security Council. Other agencies with significant homeland security responsibilities include the Departments of Health and Human Services, Justice, and Energy.
Whereas the Department of Defense is charged with military actions abroad, the Department of Homeland Security works in the civilian sphere to protect the United States within, at, and outside its borders. Its stated goal is to prepare for, prevent, and respond to domestic emergencies, particularly terrorism. On March 1, 2003, DHS absorbed the U.S. Customs Service and Immigration and Naturalization Service (INS) and assumed its duties. In doing so, it divided the enforcement and services functions into two separate and new agencies: Immigration and Customs Enforcement and Citizenship and Immigration Services. The investigative divisions and intelligence gathering units of the INS and Customs Service were merged forming Homeland Security Investigations, the primary investigative arm of DHS. Additionally, the border enforcement functions of the INS, including the U.S. Border Patrol, the U.S. Customs Service, and the Animal and Plant Health Inspection Service were consolidated into a new agency under DHS: U.S. Customs and Border Protection. The Federal Protective Service falls under the National Protection and Programs Directorate.