When a Tunisian-born man drove a 19-ton rented truck into a crowd of revelers celebrating France’s national holiday in the Mediterranean town of Nice last week, killing 84 people and injuring hundreds more, it was a deadly new example of an old terrorist tactic of turning vehicles into weapons, according to Stanford experts.

French authorities identified the man behind the wheel as Mohamed Lahouaiej Bouhlel, a 31-year-old immigrant from Tunisia who had lived in France since around 2005 and had been working as a delivery driver. Police shot him dead on the scene.

Martha Crenshaw, a senior fellow at Stanford’s Center for International Security and Cooperation (CISAC), said the fact that Bouhlel already had a commercial driver’s license gave him easy access to his weapon of choice.

“It was just unfortunate that he was somebody who already drove big trucks,” said Crenshaw.

“He did not have to go do something special, like train for a pilot’s license in the way that the 911 hijackers did, in order to acquire the means to kill people.”

Vehicles as tools of terror

Crenshaw said there had been around 30 incidents worldwide since 1994 where terrorists used vehicles as their primary weapon in attacks on civilians (not including car and truck bombs where explosives were used). Crenshaw noted that not all those vehicle attacks caused casualties.

If you include assaults on police and military targets, there have been more than 155 attacks where a vehicle has been used as a weapon in the way the truck was used in Nice, with over 75 of those attacks occurring in just the last three years, according to data from the National Consortium for the Study of Terrorism and Responses to Terrorism (START).

However, the exceptionally high number of casualties puts the attack in Nice in a league of its own. Most of the vehicle attacks on police and military only result in one or two casualties at a checkpoint or other hard target.

Stanford terrorism expert and former U.S. Special Forces Colonel Joe Felter said he was concerned that the attack in Nice “lowered the threshold” for aspiring terrorists who would be motivated to carry out copycat attacks.

“This was a disturbingly effective attack,” said Felter, a senior research scholar at CISAC.

“The message for would-be terrorists is that you don’t have to become a bomb maker to successfully execute a mass casualty attack. With a driver’s license and a credit card you can weaponize a rental truck.”

A challenge for law enforcement

Former CISAC fellow Terrence Peterson said it would be particularly difficult for law enforcement agencies to prevent terrorists from gaining access to vehicles.

“The types of people who would show up on other lists…like the no-fly list, are not going to show up when they rent a car,” said Peterson.

“A car is such a mundane object. How do you control using an everyday object for a terrorist attack? It’s nearly impossible.”

Al Qaeda had previously advocated using pickup trucks to target civilians, in the “Open Source Jihad” section of its propaganda magazine “Inspire.”

“The idea is to use a pickup truck as a mowing machine, not to mow grass but mow down the enemies of Allah,” according to a translation on the Web site MEMRI Cyber and Jihad Lab, which tracks jihadist postings online.

The article also advised would-be terrorists to, “pick your location and timing carefully. Go for the most crowded locations. Narrower spots are also better because it gives less chance for the people to run away…Therefore, it is important to study your path of operation before hand.”

French prosecutors said that Bouhlel carried out surveillance of the Promenade des Anglais prior to his attack there, and that he conducted online research into the mass shootings in Orlando and Dallas.

Murky motivations

It is still unclear what motivated Bouhlel. He had a history of domestic violence, psychological problems and money troubles, according to media reports. Acquaintances said the divorced father of three was not an outwardly religious Muslim. He reportedly drank alcohol, used drugs, ate pork and had sexual encounters with other men, all of which are forbidden under strict interpretations of Islam.

However, French authorities have suggested that he may have undergone a rapid conversion to radical Islam. And a Web site affiliated with the terror group ISIS has claimed Bouhlel as “a soldier of the Islamic State.”

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The apocalyptic ideology of jihadist groups like the Islamic State (also known as “Daesh”) could be particularly appealing to “petty criminals, psychologically deranged or otherwise lost souls” such as Bouhlel, said David Laitin, James T. Watkins IV and Elise V. Watkins professor of Political Science.

“Spurred by Salafist propaganda, these recruits can work privately, away from any institutional connection with Daesh, to cause horror,” Laitin said.

“And many police forces are out of touch with vulnerable populations and are slow to identify potential recruits.”

"Confrontation is unavoidable"

Regardless of Bouhlel’s motivation, his attack would likely bolster the anti-immigrant agenda of France’s far-right political parties such as the National Front, which advocate policies such as closing the borders, exiting the European Union and deporting bi-nationals with links to Islamist groups, said Cécile Alduy, associate professor of French and an affiliated faculty member with the Europe Center at the Freeman Spogli Institute for International Studies.

“The attacks will only strengthen the feeling that the political elites in power failed, and that the National Front “told us so” and are the only ones left to trust,” Alduy said.

Patrick Calvar, the head of France’s counter-terrorism intelligence agency DGSI, warned earlier this year that the recent series of terror attacks on French soil could trigger “inter-ethnic clashes” between far-right vigilante groups and Muslims living in France.

“One or two more terrorist attacks” and “the confrontation [between the two sides] is unavoidable,” said Calvar.

Alduy said she feared the shift in French public opinion could make Calvar’s prediction more likely.

“An opinion poll…in March 2015 put “sadness” as the primary feeling that respondents identified with following the Charlie Hebdo attacks,” Alduy said.

“After the November attacks, it was “anger”, with “hatred” following closely for over 60% of them. Now what will it be?”

A British exit from the European Union would slow economic growth, reduce Europe's impact in world politics, and strengthen regimes such as Russia's that prefer a weaker, less united Europe, Stanford expert Christophe Crombez says.

Stanford scholar Kenneth Scheve says history shows that mass mobilizations and changing tax fairness norms were key factors behind higher tax rates for the wealthy based on the premise that if labor is conscripted, the wealthy should pay their share, too.

U.S. and European societies tax the rich at higher rates when people believe that the wealthy have unfair privileges due to their economic status, a Stanford professor said.

Kenneth Scheve, a professor of political science and senior fellow at the Freeman Spogli Institute for International Studies, recently published a book, Taxing the Rich: A History of Fiscal Fairness in the United States and Europe, with co-author David Stasavage, a New York University political scientist.

Scheve studies international and comparative political economy and comparative political behavior. The Stanford News Service interviewed him about the issue of taxes, the wealthy and inequality.

What are the historical origins behind the decisions for countries to impose high taxes on the rich?

The real watershed for taxing the rich came in 1914.  Before that time, even among countries who adopted income taxes, the rates on high earners never exceeded 10 percent. Most countries had some sort of inheritance tax, but rates were never above 15 percent. Among the countries that mass-mobilized for World War I, this changed dramatically with countries adopting top income tax rates that exceeded 70 percent during and immediately after the war. These increases were repeated during World War II with top rates in some countries exceeding 90 percent. We show in the book that these decisions had more to do with changing beliefs about tax fairness and preserving equal sacrifice in the war effort than simply that the wars were expensive. It was not the most financially desperate countries that taxed the rich the most. Democratic countries for which equality fairness norms were the strongest tended to respond to mass mobilization with higher taxes on the rich much more so than non-democracies.

What does your book debunk – what is its most surprising finding?

The two most commonly held ideas about when and why countries tax the rich are when they democratize and when inequality is high. We find surprisingly little evidence for either one of these ideas. The latter finding is particularly important for understanding what’s happening today in countries like the United States that have high and rising economic inequality. A common question is, “Why hasn’t the political system responded with higher taxes on the rich?” In sorting out which answers to this question are compelling, it is critical to understand that this lack of response is not unusual historically, and so answers that emphasize specific purported shortcomings in contemporary American democracy may be misleading.

Do high taxes on the rich actually reduce inequality between the rich and poor?

The short answer is yes. We found that the countries which, for whatever reason, raised taxes on income and wealth subsequently had lower levels of income and wealth inequality. The longer answer is that this finding comes with some caveats. It is hard to identify factors that lead countries to change their tax policies that wouldn’t also influence inequality, making it difficult to isolate the impact of high taxes on inequality.

What roles do war and technology play on the imposition of high taxes on the richest segment?

We found that it is not just war but mass-mobilized wars, often with conscripted armies, that lead countries to impose high taxes on the rich. Technology has played a decisive role in whether countries can and want to fight wars with mass armies in which a substantial proportion of the population is mobilized. It was not possible to transport, supply, and command these armies until the railroad and other technologies of the industrial revolution were developed, and once militaries could employ technologies such as cruise missiles that allowed them to deliver force at a distance with precision, mass armies became much less desirable. The late 19^th to the mid-20^th century was the era of the mass army and, in many ways, the era of high taxation on incomes and wealth.

Looking ahead, what do you expect to be the future tax burden for those at the top of income and wealth levels?

We should not expect a return to the high top tax rates of the post-war era. Future wars are more likely to be fought with drones and professional soldiers than mass armies. Absent the new fairness arguments that mass-mobilized wars made credible, it is not clear that in most countries, including the United States, there is likely to be a consensus that taxing income and wealth at substantially higher levels is fair. This is the lesson that we draw from history, and it also fits with what many American voters prefer today. When we have conducted surveys on representative samples of Americans, we have found only minority support for implementing a tax schedule radically more progressive than the one in place today.

We do find, however, that citizens care a great deal about tax fairness and there is substantial support for some tax reforms that resonate with a variety of competing visions for what counts as a fair tax system. For example, in the current U.S. tax system, in some instances the rich actually pay a lower rate of tax than everyone else.  Reforms to address these privileges seem both desirable and a reasonable expectation for future policy.