U.S. Deparment of Homeland Security is a Cabinet department of the United States federal government which is focused on homeland security to ensure a homeland that is safe, secure, and resilient against terrorism and other hazards. U.S. Department of Homeland Security combines 22 different federal departments and agencies into a unified, integrated cabinet agency. Their mission to secure the nation requires the dedication of more than 225,000 employees in jobs that range from aviation and border security to emergency response from cyber security analyst to chemical facility inspector. The foundation of national homeland security strategy designed to achieve homeland security relies on the three key concepts of security; resilience; and customs and exchange. In turn, these key concepts drive broad areas of activity that the Quadrennial Homeland Security Review (QHSR) process defines as homeland security missions. Their main areas of responsibility are Guarding against Terrorism; Securing their Borders; Enforcing their Immigration Laws; Improving their Readiness for; Response to and Recovery from Disasters; and Maturing and Unifying the Department. U.S. Deparment of Homeland Security was established in 2002.