A death squad is an extra-judicial group whose members execute or assassinate persons they believe to be politically unreliable or undesirable. Such armed groups have been employed by governments of many political ideologies to kill political opponents or anyone suspected of supporting an armed or unarmed insurgency group. Dictatorships, especially totalitarian ones, have often used them to kill whole groups of people who do not fit their political ideology, religion, or race: see Genocide

Death squads were common in Central America during the 1980s. Many of them were believed to be employed by various governments. The Central American death squads often consisted of members of the national armed forces and often acted in close cooperation with the highest officials of the military. Many of these death squads hunted down leftist rebels and suspected supporters in the countryside, killing their victims, and occasionally wiping out whole villages.

In El Salvador, the death squads achieved notoriety for the murder of Archbishop Óscar Romero and the murders of four American nuns. This prompted great controversy and outrage in the US due to the death squads' allegedly close ties to El Salvador's US-supported government.

There have been other murderous death squads throughout history. During the late 1930's the Soviet government under Joseph Stalin used death squads in the secret police force, the NKVD, to hunt down and kill hundreds of thousands of known or suspected political opponents during the Great Purge. Many were innocent bystanders caught by mistake or misidentified. According to some estimates, more than 1 million victims were killed, mostly by being shot; millions more were sent to gulags.

When Nazi Germany launched a massive invasion of the Soviet Union in 1941, the Nazis brought along four traveling death squads called Einsatzgruppen to hunt down and kill Jews in the occupied areas; this was the first of the massive masscres of the Holocaust. Typically the victims, which included many women and children, were forcibly marched from their homes to open graves or ravines before being shot. Many others suffocated in specially designed poison trucks called gas vans. Between 1941 and 1944, the Einsatzgruppen killed about 1.2 million Soviet Jews, as well as tens of thousands of Soviet leaders, POWs and Gypsies.

The Khmer Rouge began employing death squads to purge Cambodia of non-Communists after taking over the country in 1975. They rounded up their victims, questioned them, and then took them out to killing fields to be shot or beaten to death. More than 1.6 million Cambodians fell victim before the Khmer Rouge was overthrown.

In Northern Ireland, Loyalist death squads, supported by the British military, have been blamed for the deaths of Irish Republicans as part of a campaign of terror.

The Rwandan Genocide of 1994 was carried out by numerous death squads called the Interahamwe see History of Rwanda. Members of these killing squads hunted down Tutsis and moderate Hutus in many towns and villages. The Interahamwe typically chopped up their victims with machetes or shot them at close range. The Rwandan Hutu armed forces often helped in these massacres, which killed from 650,000 to 800,000 before the Rwandan Patriotic Front took over the country in July of that year.

In the late 1990s, the Clinton administration alleged the use of paramilitary death squads by Serb warlords and by Slobodan Milosevic in Kosovo as a pretext to launch a bombing campaign against Yugoslavia. As predicted, the bombing campaign, which targeted civilian infrastructure, including bridges, government buildings, radio stations and the Chinese embassy caused huge flows of refugees. Graphic reports of disorganized genocide which were used as propaganda to move Europe and the US populations, were subsequently proved to be unfounded. After the war's end, no evidence for genocide was found; the casualties before the beginning of the bombing campaign consisted of 2000 dead: 1500 Albanians and 500 Serbs who died during civil unrest in which the Kosovar separatist terrorist Kosovo Liberation Army conducted attacks agains Serb police stations and the Yugoslavian government conducted counteroperations against the attacks. See Kosovo War and [The Humanitarian Bombing Campaign (http://eha.no-ip.org/tiki/tiki-index.php?page=Kosovo%3A+The+Humanitarian+Bombing+Campaign)].

During the 2003 invasion of Iraq, U.S. officials used the term death squad to describe fedayeen paramilitary forces loyal to Saddam Hussein's regime who used guerrilla tactics to fight US and UK troops. Saddam Hussein himself had employed death squads, known as Fedayeen Saddam, to kill tens of thousands of Shiite Arabs and Kurds during rebellions he crushed in 1988 and 1991.