United States Department of Homeland Security in the context of "Homeland security"

Science, technology, engineering, and mathematics (STEM) is an umbrella term used to group together the related technical disciplines of science, technology, engineering, and mathematics. It represents a broad and interconnected set of fields that are crucial for innovation and technological advancement. These disciplines are often grouped together because they share a common emphasis on critical thinking, problem-solving, and analytical skills. The term is typically used in the context of education policy or curriculum choices in schools. It has implications for workforce development, national security concerns (as a shortage of STEM-educated citizens can reduce effectiveness in this area), and immigration policy, with regard to admitting foreign students and tech workers.

There is no universal agreement on which disciplines are included in STEM; in particular, whether or not the science in STEM includes social sciences, such as psychology, sociology, economics, and political science. In the United States, these are typically included by the National Science Foundation (NSF), the Department of Labor's O*Net online database for job seekers, and the Department of Homeland Security. In the United Kingdom, the social sciences are categorized separately and are instead grouped with humanities and arts to form another counterpart acronym HASS (humanities, arts, and social sciences), rebranded in 2020 as SHAPE (social sciences, humanities and the arts for people and the economy). Some sources also use HEAL (health, education, administration, and literacy) as the counterpart of STEM.

Mass murder is the violent crime of killing a number of people, typically simultaneously or over a relatively short period of time and in close geographic proximity. A mass murder typically occurs in a single location where one or more persons kill several others. Data suggests that approximately 30% of mass murderers die in the act.

In the United States, Congress defined mass murders as the killing of three or more persons during an event with no "cooling-off period" between the homicides. The Investigative Assistance for Violent Crimes Act of 2012, passed in the aftermath of the Sandy Hook Elementary School shooting, clarified the statutory authority for federal law enforcement agencies, including those in the Departments of Justice and Homeland Security, to assist state law enforcement agencies, and mandated across federal agencies a definition of "mass killing" as three or more killings during an incident.A mass murder may be further classified as a mass shooting or a mass stabbing. Mass murderers differ from spree killers, who kill at two or more locations with almost no time break between murders and are not defined by the number of victims, and serial killers, who kill people over long periods of time.

A border wall has been built along portions of the Mexico–United States border in an attempt to reduce illegal immigration to the United States from Mexico. The barrier is not a continuous structure but a series of obstructions variously classified as "fences" or "walls".

Between the physical barriers, security is provided by a "virtual fence" of sensors, cameras, and other surveillance equipment used to dispatch United States Border Patrol agents to suspected migrant crossings. In May 2011, the Department of Homeland Security (DHS) said it had 649 miles (1,044 km) of barriers in place. A total of 438 miles (705 km) of new primary barriers were built during Donald Trump's first presidency, dubbed the "Trump wall", though Trump had repeatedly promised a "giant wall" spanning the entire border and that Mexico would "pay for the wall," neither of which were done. The national border's length is 1,954 miles (3,145 km), of which 1,255 miles (2,020 km) is the Rio Grande and 699 miles (1,125 km) is on land.

The President's Daily Brief, sometimes referred to as the President's Daily Briefing or the President's Daily Bulletin, is a top-secret document produced and given each morning to the president of the United States; it is also distributed to a small number of top-level US officials who are approved by the president. It includes highly classified intelligence analysis, information about covert operations, and reports from the most sensitive US sources or those shared by allied intelligence agencies. At the discretion of the president, the PDB may also be provided to the president-elect of the United States, between election day and inauguration, and to former presidents on request.

The PDB is produced by the director of national intelligence, and involves fusing intelligence from the Central Intelligence Agency, the Defense Intelligence Agency, the National Security Agency (NSA), the Federal Bureau of Investigation (FBI), the Defense Department, Homeland Security and other members of the U.S. Intelligence Community.

The United States Immigration and Customs Enforcement (ICE; pronounced "ice") is a federal law enforcement agency under the supervision of the United States Department of Homeland Security. Its stated mission is to conduct criminal investigations, enforce immigration laws, preserve national security, and protect public safety. ICE was created as part of the Homeland Security Act of 2002 following the September 11 attacks. It absorbed the prior functions of the Immigration and Naturalization Service and the United States Customs Service.

ICE has been involved in multiple controversies throughout its existence, with significant increases in criticism during the first and especially the second administration of Donald Trump. Following the passage of the One Big Beautiful Bill Act in 2025 as part of Trump's hardline immigration policy, ICE became the largest and most well-funded federal law enforcement agency in U.S. history. Its aggressive and anonymized enforcement actions, controversial publicity campaigns, and militarization resulted in significant drops in public support and raised concerns over legality, lack of accountability, and civil rights violations. ICE agents are noted for wearing masks, civilian clothing, and using unmarked vehicles to protect their identity. The agency has been the subject of widespread protests particularly in 2018 and 2025, with some activists calling for its abolition. Since its expansion, the agency has been described by critics, as well as the American Civil Liberties Union, as a growing paramilitary force under Trump's personal control.

The federal government of the United States empowers a wide range of federal law enforcement agencies (informally known as the "Feds") to maintain law and public order related to matters affecting the country as a whole.

While the majority of federal law enforcement employees work for the Department of Justice and Homeland Security, there are dozens of other federal law enforcement agencies under the other executive departments, as well as under the legislative and judicial branches of the federal government.

George W. Bush's tenure as the 43rd president of the United States began with his first inauguration on January 20, 2001, and ended on January 20, 2009. Bush, a Republican from Texas, took office after defeating the Democratic incumbent vice president Al Gore in the 2000 presidential election. Four years later, he won re-election in the 2004 presidential election, after defeating the Democratic nominee John Kerry. Alongside Bush's presidency, the Republican Party also held their majorities in the House of Representatives and the Senate during the 108th and 109th U.S. Congresses following the 2002 and 2004 elections, thereby attained an overall federal government trifecta. Bush was constitutionally limited to two terms and was succeeded by Democrat Barack Obama, who won the 2008 presidential election against Bush's preferred succcessor, John McCain. He is the eldest son of the 41st president, George H. W. Bush.

A decisive event reshaping Bush's administration were the terrorist attacks on September 11, 2001. In its aftermath, Congress created the Department of Homeland Security and Bush declared a global war on terrorism. He ordered an invasion of Afghanistan in an effort to overthrow the Taliban, destroy al-Qaeda, and capture Osama bin Laden. He also signed the controversial Patriot Act in order to authorize surveillance of suspected terrorists. In 2003, Bush ordered an invasion of Iraq, alleging that the Saddam Hussein regime possessed weapons of mass destruction. Intense criticism came when neither WMD stockpiles nor evidence of an operational relationship with al-Qaeda were found. Before 9/11, Bush had pushed through a $1.3 trillion tax cut program and the No Child Left Behind Act, a major education bill. He also pushed for socially conservative efforts, such as the Partial-Birth Abortion Ban Act and faith-based welfare initiatives. Also in 2003, he signed the Medicare Prescription Drug, Improvement, and Modernization Act, which created Medicare Part D.

United States Customs and Border Protection (CBP) is the largest federal law enforcement agency of the United States Department of Homeland Security. It is the country's primary border control organization, charged with regulating and facilitating international trade, collecting import duties, as well as enforcing U.S. regulations, including trade, customs, and immigration. CBP is one of the largest law enforcement agencies in the United States. It has a workforce of more than 45,600 federal agents and officers. It is headquartered in Washington, D.C.