On September 11, 2001, the United States was subject to a series of terrorist attacks that killed an estimated 3,000 people after hijacked airliners crashed into the Twin Towers of the World Trade Center in New York City; the Pentagon; and a field in Pennsylvania. (see generally September 11, 2001 Digital Archive, Center for History and New Media/American Social History Project). On the evening of September 11, President Bush addressed the nation, saying in part:

Today, our fellow citizens, our way of life, our very freedom came under attack in a series of deliberate and deadly terrorist acts. The victims were in airplanes or in their offices. Secretaries, business men and women, military and federal workers. Moms and dads. Friends and neighbors. Thousands of lives were suddenly ended by evil, despicable acts of terror. The pictures of airplanes flying into buildings, fires burning, huge structures collapsing, have filled us with disbelief, terrible sadness and a quiet, unyielding anger. These acts of mass murder were intended to frighten our nation into chaos and retreat. But they have failed. Our country is strong. A great people has been moved to defend a great nation.

In an address to a joint session of Congress on September 20, the President gave an ultimatum to the Taliban regime in Afghanistan to deliver to United States authorities all the leaders of the al Qaeda group, and announced a series of other initiatives, including measures to strengthen domestic security. On October 7, military action against the Taliban was commenced under "Operation Enduring Freedom" and two months later the last major city in Afghanistan was taken by forces of the U.S and 26 other nations participating in its military coalition. On October 26, President Bush signed the USA Patriot Act (USAPA) into law, giving federal authorities sweeping new powers to investigate and prosecute potential terrorism suspects, including stronger authority to conduct surveillance activities and to detain individuals without formal charges.

While polls indicated strong public support for the Bush Administration's counter-terrorism initiatives, concerns were raised in the Congress and by leading civil rights advocates that some of the proposed domestic measures jeopardized personal liberties. In April 2002, a lawsuit, Turkmen v. Ashcroft, was filed alleging that the Department of Justice and the Immigration and Naturalization Service violated the rights of hundreds of mostly Arab or Muslim individuals, including many recent immigrants, who were picked up and subjected to detention after September 11th. Among the charges included in the complaint were that federal law enforcement authorities were using alleged immigration violations as an illegal pretext for arrests prior to a thorough criminal investigation, and that keeping the detainees in jail past the date at which they could be deported violated Fifth Amendment due process rights for both citizens and non-citizens. Several other cases also challenged various actions under the broadened anti-terrorism authority. See generally Civil and Criminal Terrorism Cases, Findlaw.com.

Less than a month after September 11, the President also issued an Executive Order establishing a Council for Homeland Security to coordinate domestic counter-terrorism efforts and named Pennsylvania Governor Tom Ridge as executive director of the Council. Subsequently, in June 2002, the President announced his support for the creation of a new Cabinet-level Department of Homeland Security to consolidate various federal agencies and programs in a single department. After prolonged debate in the Congress, legislation establishing the Department was approved by the Congress and signed into law by the President on January 24, 2003, with Mr. Ridge named to head the Department.