PARIS—In Paris, church bells clang against the squawk of police sirens. Security forces of every stripe patrol the Jewish quarter in the Marais neighborhood, watching over tourists posing by the Louvre’s pyramid and hovering near the doors of the city’s landmark hotels and boutiques. Even as Paris prepares to empty out just as it does every August, leaving its cobbled streets to dwindling numbers of tourists, it is a city on guard.

The recent, deadly Bastille Day rampage through a seaside boulevard in Nice and the summary execution of an elderly Catholic priest in a village in Normandy have kept the country in the state of emergency President Francois Hollande instituted last November, following the coordinated attack in Paris that left 130 people dead. Heavily armed police now patrol the streets. “What can we do? Stay home?” asked one older man who declined to give his name, waiting in line by the Seine to collect boules for a game of pétanque. “We have to keep moving, keep living, otherwise, what is the point?”

France and the rest of Europe have endured this near state-of-siege before. Older Europeans can recall a time when communists, nationalists, anarchists, Islamists, and international criminals wrought havoc on the continent. Palestinian terrorists shattered the harmony of the 1972 Summer Olympics in Munich, taking hostage and murdering 11 Israeli athletes. Italian communists kidnapped and murdered a former prime minister in 1978. In 1988, Libyan terrorists brought down Pan Am flight 103 over Lockerbie, Scotland, killing 270 people. Through the 1970s and into the 1980s, warring Palestinian factions and Iranian revolutionaries turned Europe into a battleground for settling internal feuds and assassinating enemies, opening fire on the Rome check-in counter for the Israeli airline El Al, and hijacking planes. In France itself, an Algerian Islamist group that had fought the Algerian government during the civil war in 1991 bombed Paris metro stations, a Jewish school, and L’Arc de Triomphe. Hezbollah, as part of its declared aim to expel any French or American presence from Lebanon, conducted at least five bombings on French soil between 1985 and 1986. Armenian terrorists, seeking vengeance for the Armenian Genocide, struck the Orly airport in 1983, killing at least five people.

As Europe grapples with a wave of attacks either conducted or inspired by the Islamic State, the violence and tension the continent now faces have been dubbed a “new normal.” Yet it is a problem with a precedent. And how Europeans dealt with and ultimately overcame their terrorism problem in the past could bear lessons for how they deal with it in the future.

Despite the obvious ideological and strategic differences between ISIS and the threats of decades past, local law enforcement agencies across Europe can still draw on the tactical lessons of that previous age. To crack down on the possible movement of suspected bomb material by the Irish Republican Army (IRA), the Belfast police established checkpoints and searched cars and their drivers, for example. In the 1970s, authorities set up a “ring of steel” around the city center to prevent private cars from entering. Even then, of course, attacks persisted.

Even as violence continued in Ireland and across Europe in the 1970s and 1980s, security agencies knew who the major terror groups, what motivated them, and what warning signs to look for in advance of an attack. For example, when the IRA was launching attacks in Britain, authorities “could comfortably know that they would have almost all of the countermeasures within their purview,” Michael Connolly, the director for military and veteran affairs at the Robert H. Smith School of Business at the University of Maryland, explained. “They were also able to share intelligence among their own agencies, [and] implement checkpoints. … The complications in trying to do this among different countries, borders, militaries, and governments [today] are mind-boggling.”

Francisco de Borja Lasheras, the head of the Madrid office for the European Council on Foreign Relations, agreed. From as early as 1960, Spanish cities dealt with repeated attacks from Basque separatists, who sought independence from Spain. “The Basque represented a certain part of the population that you could eventually mitigate and neutralize, even if the conflict and the political question” remained, he said.

To counter the separatists, Spanish authorities resisted sending in armed forces, instead making it solely an internal law enforcement and domestic counter-terrorism issue. As long as separatism was treated as a political problem addressed with local support, political solutions could be found. Eventually, the Basque separatists lost the loyalty of many Spaniards as it escalated its carnage. Many of its members were arrested, and in the end the organization ended its armed campaign and chose to pursue political negotiations.     

Today, politicians in Western and Central Europe have stiffened their internal security measures and cracked down on border controls. European Union ministers have touted a plan that would give governments access to digital intelligence, including criminal records and airline passenger data, from telecommunications and digital service providers. France’s state of emergency, meanwhile, has entered its ninth month. Germany, following the Munich shooting, has tightened security on its borders with countries like the Czech Republic, while neighboring Austria has beefed up measures on its side of the line, too. Germany’s interior minister is now also proposing a plan to strip dual nationals of their German citizenship if they fight for terror groups, making it easier to deport them. The Austrian government has also sent some of its elite “Cobra” operatives to help Germany with its internal investigations into terrorism.

In Britain, London’s Scotland Yard announced this month that it will deploy additional armed officers across the city to prepare for future attacks (most London police officers are unarmed). London Police Commissioner Bernard Hogan-Howe has already said that it was “a case of when, not if” the city comes under attack. Barely 48 hours after his remarks, a Norwegian man of Somali descent attacked a group of people in Russell Square in central London, stabbing and killing an American woman and wounding several others.

When it comes to unifying over policy, the European Union has always been hobbled by its member states’ preference for preserving national sovereignty. Terror laws are but one area where this has always been an issue. In 1976, in response to the hostage crisis at the Munich Olympics, the EU created the TREVI group, which was designed to combine transnational efforts to combat terrorism, train police, and maintain security at nuclear sites.

But the lessons of TREVI seem not to have stuck. Across the continent, security agencies are once again starting to communicate and share information. For the most part.  Josef Janning, a senior policy fellow at the European Council on Foreign Relations and long-time expert on European policy and global affairs, said that the new slate of threats is “something Europeans are ready to live with as a fact of life.” Since the coordinated attacks by ISIS in November, French secret service officers have launched their own operations in Brussels, the nerve center for the November plot and home to many of its attackers. But officials have stopped short of sharing everything they’ve uncovered with the Belgians, Janning said.

That’s because of the litany of errors that accompanied the aftermath of the November terror attacks in Paris, with Belgian authorities taking most of the blame. Belgian authorities failed, for example, to share data or act on the knowledge that one of the Paris attackers had been flagged by Turkish authorities and was deported to the Netherlands. Better policing in Belgium might have interdicted the plethora of guns that flooded the black market after the Balkans war, allowing the Paris attackers to easily purchase powerful weapons. The French believe “their Belgian counterparts were not effective enough in monitoring what was actually going on in Brussels,” particularly in neighborhoods like Mollenbeek, Janning said.  

In the past, local informants and amnesty programs worked with law enforcement and intelligence officials to root out militants, helping bring down groups like the Red Brigades, a left-wing Italian militia. Modern terror cells would be dismantled in the same way that underground organized crime rings are, Janning said, with law enforcement drilling down into communities and neighborhoods and working their local connections to gather intelligence. Ideologies would need to be combatted in classrooms and online chatrooms. Agencies, he said, would need to talk to each other to track the movement of people, goods, and weapons, across districts, cities, and borders. But this all remains a work in progress.

To give European security agencies the forensic capacity to do any of this, however, it must be willing to expand its internal security apparatus. “Germany and other European countries will become a lot more like Britain where you have surveillance cameras in public places almost everywhere,” Janning said.

As Vidhya Ramalingam, co-founder of Moonshot CVE, a tech startup specializing in countering violent extremism, argued, at present, government technology that could help expand surveillance is being poorly deployed “Data-gathering capability is currently being used by governments and private institutions to identify violent extremists, but only for the purposes of take-downs, arrests, and prosecutions,” Ramalingam said. “This data can be mined and used for the purposes of intervention. Before an individual becomes a terrorist, they may drop clues in the online world that they are going down this path. If we can use these clues to identify them, before they cross the line, engage with them and seek to change their behavior, we can prevent the next generation of vulnerable individuals from becoming terrorists.”

In the end, Europe knows only too well the climate of perpetual chaos that ISIS and its adherents seek to engender. Sowing a climate of mass hysteria is central to its long game, keeping societies brittle and on edge, distrustful of the governments and security forces pledging to protect them. As Lasheras explained, the European terrorists of previous decades, including groups like the Red Army Faction and the Red Brigade, pursued similar ends. These “terrorists were the anarchists who were blowing up politicians in Paris and Spain … the use of mass hysteria and the attempts to polarize and settle grievances real or perceived, in that regard, it’s not that new.”

Today, the greatest challenge facing Europe is that, unlike in times past when groups would visit terror upon the continent, ISIS speaks to the disaffected living inside a wider population—those who bear grievances separating them from the mainstream. Security officials have to contend with finding the few aggrieved among the many. And unlike past nationalist threats, identifiable through certain social traits and behavior, much of the inspiration for lone wolves fighting for ISIS is imported, often from the battlefields of Syria and Iraq.

There are, of course, numerous ways in which the attacks of today differ from those of decades past. Groups like the IRA were motivated by defined goals related to governance and territory. ISIS, on the other hand, “has a stated goal of trying to expand, through terrorism, until they have brought about the end of times,” Connolly said. It has also repeatedly declared that as long as the governments of France, Germany, and other European nations participate in the coalition bombing ISIS targets in Iraq and Syria, citizens of those countries should expect more attacks at home.

Beppe Severgnini, a columnist for the Italian newspaper Corriere della Sera, has been more optimistic. Writing in The New York Times after the Paris attacks in November. “Twenty-five years after the last era of terror, our generation—the generation that witnessed and weathered it—has a duty to remind our children what worked against terrorism and, in the end, defeated it.” Europeans, Severgnini wrote, must continue today as they did in decades past. “[W]e youngsters went on studying, working, playing, falling in love and traveling—across Europe and beyond. We refused to let a bunch of psychopaths derail our lives. And we won. Our children will win, too.”