To everyone watching the surge in far-left violence across the West and telling themselves it cannot get worse: I am old enough to remember when organized left-wing terror groups were killing, kidnapping, and bombing across Europe and America. The 1970s and 1980s are worth a quick revisit. In West Germany, the Marxist-Leninist Red Army Faction (Baader-Meinhof) and the Revolutionary Cells carried out hundreds of bombings, arson attacks, and bank robberies over some 25 years, wounding hundreds and killing dozens. In September 1977, Baader-Meinhof ambushed Hanns Martin Schleyer, one of Germany’s top industrialists, murdered his driver and three police officers, held him for 43 days, then killed him. In Italy, the Marxist-Leninist gang Red Brigades carried out assassinations, kneecappings, and kidnappings over 20 years, killing nearly fifty people. In 1978 they kidnapped former prime minister Aldo Moro, killed his five bodyguards, and left his body in a car trunk after 54 days. In Spain, GRAPO, another Marxist-Leninist group, killed more than 80 people, including a notorious 1979 cafe bombing in Madrid. It used kidnappings to attack the state and later raise money. Its highest profile victims were the president of the Council of State and a top military general. In France, Action Directe, a self-described “libertarian communist urban guerrilla” group, carried out more than 80 bombings. Its leaders were convicted of assassinating General René Audran in 1985 and Renault CEO Georges Besse in 1986. In America, the Weather Underground claimed roughly two dozen bombings, including the Capitol and the Pentagon. Their bombs killed no one but their own members—three in a Greenwich Village townhouse in 1970—until 1981, when remnants joined the Black Liberation Army in the Brink’s robbery. A guard and two police officers died. These groups did not emerge from nowhere. They began inside much larger movements of protest marches, campus organizing, and anti-war activism. Small cells decided that talking had failed, that the state was illegitimate, and that violence was the only remaining language. They were few in number but they did real damage. The grievances of the 1970s were not identical to today’s. The mechanics of escalation, though, are similar. When political anger, economic frustration, and a sense of moral emergency pile up, it only takes a handful of people to break away and treat armed confrontation as the next logical step. History shows it has happened before. The question is whether it will happen again.