The Paris bombs exploded in the most ordinary places at the busiest times.

A post office. A driver’s license bureau. A shopping center cafeteria. A restaurant on the Champs Elysees. A Tati discount clothing store, where five died and 51 lay wounded. Parisians spoke of their anxiety. The French prime minister called it “war.”

These were the crisp autumn days of 1986, when the French capital reverberated with blasts — nearly two dozen in nine months, including five explosions in just 11 days, most with origins in the politics of the Middle East. Authorities warned residents and tourists to stay away from crowded places, as if that were possible in a city of 8 million.

No one knew quite how to react.

Places that were once safe seemed less so. It was unsettling, I wrote back then, to wander a familiar city and wonder whether the next bomb might explode nearby. Simple decisions became an imaginary game of roulette. To sit at a cafe or stay home, to take that street or another, to go to lunch now or later, to stand in line for a movie.

The questions in 1986 foreshadowed the questions now, as Parisians struggle to make sense of the assault last week that killed at least 129 people and counting. Fathoming the unfathomable, making sense of the senseless. Why now? Why us? How does this end? Does this end?

“There was a sense of danger, that people would go into the Metro and play with their lives,” said French academic Philippe Le Corre, who lived in Paris at the time. But the scale has shifted, ratcheting up the threat and the sense of unease. “My feeling after Friday is that the risk of bombs going off anywhere is much more widespread. The world has changed so much.”

Paris in the 1980s was no stranger to bombings or to civil strife. The city had always been a beacon, a symbol and a target. Plenty remembered the blood spilled in Paris during the fight for Algerian independence about 25 years earlier. The staccato wave of bombings that started in December 1985, however, set the city on edge.

The bombs were made of the plastic explosive Semtex, popular among terrorists because it was easy to use and difficult to detect. The attackers dropped the devices into trash bins or planted them in the Metro and other public places and simply walked away. At least a dozen people died, and more than 200 were injured.

Contributing to the sense of a world gone awry, assassins killed the French military attache in Beirut in September 1986 as he walked to work. Militants killed four French soldiers on peacekeeping duty and held seven French citizens hostage.

“We are fighting against madmen,” Alain Bertie, a World War II veteran, told me one day on a Paris street corner. A war without clear battle lines lay beyond his comprehension. “We have to fight, the same way we fought against the Germans.”

Yet, by the gruesome standard set by the Islamic State and other terrorist groups of more recent vintage, the bombing campaign possessed a logic that was comprehensible, if no less vile. The killers in 1986 had an objective. They wanted France to release three prisoners, including accused terrorist Georges Ibrahim Abdallah, awaiting trial in the killing of a U.S military attache and an Israeli diplomat.

Jacques Chirac, the French prime minister, who became president in 1995, declared that he would not submit to what he called blackmail. He increased police powers and tightened visa restrictions. In 1987, a French court convicted Abdallah and sentenced him to life in prison, where he remains. Police arrested suspects in the bombings. The explosions stopped.

Something similar happened in 1995, when members of an Algerian terrorist cell detonated eight bombs, including two aboard Paris commuter trains. Seven innocents died, at least 200 were wounded. There, too, the attackers had a goal: to halt French support for the government in Algiers.

The carnage was calibrated. And it ended.

Beyond specific objectives, terrorist organizations before al-Qaeda were “trying to build the popularity of their causes without being seen as wanton killers,” said Daniel Benjamin, a former State Department coordinator for counterterrorism. Earlier terrorism had “a made-for-TV look compared to what we’re seeing now,” said Benjamin, co-author of "The Age of Sacred Terror."

If al-Qaeda represented the birth of “uncalibrated, indiscriminate killing,” Benjamin said, “ISIS has sought to do them one better.” ISIS is an alternative acronym for the Islamic State.

Simond de Galbert, a onetime French diplomat, sees it the same way.

“In the 1980s, the terrorists were using attacks in a transactional manner to achieve specific French action,” said de Galbert, a visiting fellow at Washington’s Center for Strategic and International Studies. “Today, the terrorists are trying to create disunity in France, trying to turn the French against the Muslim minority, trying to create a de facto conflict of civilizations.”

If Parisians thought the January attacks on cartoonists and other journalists at the Charlie Hebdo offices in the 11th arrondissement were a one-time event, the Friday attacks showed them otherwise: “A lot of people realize the attacks in January were not an end, but the beginning of something that will last far longer," de Galbert said.

It remains entirely unclear what will satisfy the terrorists or what will stop them. In Paris now, just as in Paris three decades ago, the anger and the uncertainty melted into one. The current French president, François Hollande, like Chirac, called the attacks an act of war.

The 1980s bombing spree did not last long. Life did return to normal. People laughed and strolled and again rode the Metro without a care. But even in the calm that followed, Europe’s terrorism-trackers felt sure that the violence would return.

“They learn. We learn. We’re ahead at the moment,” Cmdr. George Churchill-Coleman, head of Scotland Yard’s anti-terrorist squad, told me in 1987, adding a prescient warning: “Don’t be too confident that everything’s under control.”

Peter Slevin, a former Washington Post diplomatic correspondent, is an associate professor at Northwestern University and the author of "Michelle Obama: A Life," released in April.

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