But while the term “enemy combatant” may seem to have been begotten by government machismo in reaction to the 9/11 terrorist attacks, the label actually goes all the way back to World War II. In recent years, the government has simply revised it.

Charles E. Tucker Jr., executive director of the International Human Rights Institute at DePaul University, said the term was first attributed to Nazi saboteurs.

In the 1942 case Ex parte Quirin, the U.S. Supreme Court upheld the constitutionality of trying eight German infiltrators in military commissions as “unlawful combatants”:

“By universal agreement and practice, the law of war draws a distinction between the armed forces and the peaceful populations of belligerent nations and also between those who are lawful and unlawful combatants. Lawful combatants are subject to capture and detention as prisoners of war by opposing military forces. Unlawful combatants are likewise subject to capture and detention, but in addition they are subject to trial and punishment by military tribunals for acts which render their belligerency unlawful.”

In the case of the Nazi saboteurs, they had shed their uniforms to surreptitiously infiltrate and threaten U.S. targets, making them unlawful combatants and thus subject to a military trial.

In 2006, the Military Commissions Act defined unlawful enemy combatants in a similar manner, primarily in relation to the lawful combatant.

“The term ‘lawful enemy combatant’ means a person who is — a member of the regular forces of a State party engaged in hostilities against the United States; a member of a militia, volunteer corps, or organized resistance movement belonging to a State party engaged in such hostilities, which are under responsible command, wear a fixed distinctive sign recognizable at a distance, carry their arms openly, and abide by the law of war; or a member of a regular armed force who professes allegiance to a government engaged in such hostilities, but not recognized by the United States.”

“The term ‘unlawful enemy combatant’ means — a person who has engaged in hostilities or who has purposefully and materially supported hostilities against the United States or its co-belligerents who is not a lawful enemy combatant (including a person who is part of the Taliban, al Qaeda, or associated forces).”

For a timeline of the history of the term “enemy combatant” in the United States, click here.

Largely on the basis of its own executive orders, the Bush administration applied the term “enemy combatant” to former Chicago gang member Jose Padilla and Yaser Esam Hamdi, who was a U.S. citizen when he was captured in Afghanistan, reportedly fighting American forces with the Taliban.

In its 2003 World Report, advocacy group Human Rights Watch said, “The use of the ‘enemy combatant’ designation appeared to be intended to circumvent the U.S. criminal justice system and its safeguard of basic rights.”

Civil rights groups often cite the cases of Padilla, who was detained for more than three years without a trial for suspected connections with al-Qaida, and Hamdi. After Hamdi was detained without being charged, he became the subject of the 2004 Supreme Court case Hamdi v. Rumsfeld. The court ruled that while the government could detain unlawful combatants, detainees with U.S. citizenship have a right to challenge their detention.

In 2005, Rep. Adam Schiff, a Democrat from California, introduced the Detention of Enemy Combatants Act, which would permit the president to detain U.S. citizens with connections to al-Qaida but would also “guarantee [detainees] timely access to judicial review.” The bill never left committee, but it made the following statement about enemy combatants:

“The term ‘enemy combatant’ has historically referred to all of the citizens of a state with which the Nation is at war, and who are members of the armed force of that enemy state. Enemy combatants in the present conflict, however, come from many nations, wear no uniforms, and use unconventional weapons. Enemy combatants in the war on terrorism are not defined by simple, readily apparent criteria, such as citizenship or military uniform. And the power to name a citizen as an ‘enemy combatant’ is therefore extraordinarily broad.”

In 2006, President George W. Bush signed the Military Commissions Act, which distinguished between lawful and unlawful enemy combatants. According to the law, lawful enemy combatants are those associated with an opposing government or other organized force who identify themselves in appearance and behavior. In short, unlawful enemy combatants are those who aren’t lawful enemy combatants.

Matthew Lippmann, a professor of criminology, law and justice at the University of Illinois in Chicago, said Bush broadly defined enemy combatants as “people who fall outside the Geneva Conventions who are at war with the United States.”

The Military Commissions Act of 2006 also specified that unlawful enemy combatants could be tried in military courts and thus were not subject to rights including habeas corpus.

In 2008, the U.S. Supreme Court ruled that prisoners have a right to habeas corpus, making that provision of the Military Commissions Act of 2006 unconstitutional.

The Obama administration officially abandoned the term “enemy combatant” last year, though it has continued holding some individuals without trial at Guantanamo Bay. It attributed continued detentions to Congressional and international law, including the Geneva Conventions.

“President Obama said no, I’m not really going to buy into the notion that this is a war,” Lippmann said. “We’re going to prosecute [detainees] in a civilian court and treat them as criminals.”

For a timeline of the history of the term “enemy combatant” in the United States, click here.