History's Worst Terrorist Groups

Terrorism is not some new social disease, it has been around a long time. One rule: these have to be non-governmental organizations. Governments are far more effective at infliction terror on their citizens than NGOs. If I allowed governments then this list would be the SS, Cheka, and the Tonton Macoute.

Brown Shirts

The Sturmabteilung, the SA. Before Hitler rose to power he organized an army of thugs to intimidate opponents. They would attack rallies by other political parties, vandalize Jewish businesses, and parade the streets beating anyone who didn't properly salute. After Hitler was elected Chancellor, the SA became a dangerous rival to the governmental terrorists, the SS. On a day known as the Night of the Long Knives, Hitler had his SA leadership arrested and executed.

Ku Klux Klan

Founded by in the Southern US by former Confederate soldiers their goal was to drive freed blacks back into powerless servitude. Their weapon of choice was the lynching.  Acts that could get a man lynched included looking at a white woman, registering to vote, and not stepping into the gutter when a white man passed on the sidewalk. The KKK still exists today and work underground with neo-Nazis and Christian Identity fanatics. Membership peaked in the 1920's at over five million.

Ribbonmen and the Orange Order

The English have been trying to control Ireland for a millennium, generally unsuccessfully. Henry II in the twelfth century, Henry VIII in the 16th, Cromwell in the 17th, and so on. A major part of these wars was for Protestant England to rid Ireland of its Catholic blight.

The Catholic defenders evolved into organizations like the Molly Maguires and the Irish Republican Army. The Orange Order gave birth to the Ulster Volunteer Force. The Troubles they caused killed thousands.

Palestine Liberation Organization

One could argue, and not be wrong, that all Arab terrorist organizations (Hamas, Hezbollah, al-Qaeda) are the step children of the PLO. They have perfected the strategy of attacking soft targets, most often with bombs.

Zealots 

Jews invented the art of Middle East terrorism 2,000 years ago with their fight against Roman occupation. Often mixed terrorism with outright civil war.  Their assassins used a strategy of dressing up as women, seducing their victims, and killing them. The Romans destroyed Jerusalem to snuff the rebellion.