BRUSSELS — Green army trucks are rumbling across the cobbled streets of Brussels. Stiff-spined soldiers are patrolling the Champs-Elysees in Paris. Italian troops are guarding the Colosseum. And critics say the years-long deployments at home are sapping the ability of these militaries to fight wars.
Taken together, the domestic deployments — to guard against terrorism — are among the largest in Western Europe since World War II. They come as European militaries are tapped to address an unusually wide range of challenges at once: a resurgent Russia, grinding conflicts in the Middle East, migration across the Mediterranean and smaller wartime deployments far from their borders.
Confronted by terrorism, European leaders rushed their armies onto their streets in the aftermath of attacks starting in 2015. Although advocates say the deployments help bolster security, the peacetime duty has stretched forces thin.
Until recently, 40 percent of Belgium's combat-ready soldiers were devoted to domestic guard duty. Some officers worry that the lack of time to practice warfare means basic skills are getting rusty. In France, the former leader of the military said last month that he quit in July in part to protest that his forces were "overheating."
President Trump has pressed NATO allies to commit more toward their own defense and to international missions, but the domestic deployments have made that a challenge. The latest sign came last month at a meeting of defense chiefs in Brussels, when the alliance fell short on pledges toward the NATO training operation in Afghanistan.
In Belgium, a country of 11 million people, military leaders say their troops are feeling the strain.
"I had machine gunners with the rifle section who didn't fire a machine gun in 16 months because they had become riflemen," said Maj. Gen. Marc Thys, commander of Belgium's land forces. "It's like asking our national team that hasn't played a game of soccer all year to go to the world championships. It doesn't work."
Until October, 1,250 Belgian soldiers were deployed across the country, guarding grand boulevards, train stations and other crowded public places that make tempting targets. The intention was to increase public safety and to give police officers more freedom to do investigative work rather than tie them up on guard duty.
The domestic deployments came as European nations struggled to find a way to protect themselves against attacks in a new era of terrorism strategies. Some recent Islamic State-inspired strikes used explosives and required large networks that could be disrupted through aggressive counterterrorism work, but other attacks were as simple as renting a truck and plowing it into a crowd.
Proponents of the military approach say that such attacks can be prevented by quick-thinking soldiers. They point to June's attempted attack in the Brussels Central railway station, where soldiers patrolling the platforms shot dead a suspected bomber after he set off a small explosive that failed to hurt anyone.
"We weren't ready for the threats that we were facing," Belgian Defense Minister Steven Vandeput said about the aftermath of the 2015 terrorist attacks in Paris. Both the January Charlie Hebdo newspaper attack and the November Bataclan nightclub attack that year had Brussels connections, and authorities were searching for a quick solution.
"After November, the threat was high and at the same time police need to do police work," Vandeput said. "If we're not able to contribute to our defense, how can we contribute to others' defense?"
France also deployed soldiers to its streets following the terrorist attacks and has faced similar challenges. Italian troops have been deployed since 2008. Britain made such deployments an option this year, but it has done so sparingly. In the United States, federal law generally forbids military deployments for law enforcement purposes, although state National Guards have more flexibility when commanded at a state level.
Germany has also been struck repeatedly by small-scale terrorist attacks, and its Parliament recently considered a measure to allow the army to be used domestically. That would have been a significant step because the country's World War II history has made lawmakers wary of using their military at home. In the end, the legislature took no action.
In Belgium, the soldiers do not have the power to make arrests or investigate crimes. Advocates say their powerful rifles serve as a deterrent as they walk through crowded weekend markets or stand watch at train stations during rush hour.
"The issue has never been to keep them forever. The idea is to keep them as long as necessary," said Saad Amrani, a senior policy adviser with the Belgian Federal Police. "Some countries are used to violence and terrorism. We were not used to that type of violence."
But because the number of war-ready Belgian soldiers is small, that meant that many troops were deploying up to six months a year. Even during a domestic assignment, troops do not live on base with their families. Instead, they patrol for long hours and, they say, they have few chances to rest. Some have complained of cramped barracks and poor bathroom facilities, a consequence of the crunched budget.
Critics of the deployment also say that the security value is limited.
The real reason soldiers are on the streets, some of them say, is to give Belgian citizens the feeling their leaders are fighting terrorism. The deployment has been popular, sending the domestic approval ratings of the military skyrocketing.
"They've been standing in front of buildings, doing everything other than what they trained for," said Wally Struys, a professor emeritus of defense economics at Belgium's Royal Military Academy, who has studied the deployments. "These are very good PR operations."
Belgian authorities slimmed the deployment in October to 1,000 soldiers, giving troops a bit more breathing room between stints in the street.
"The worst part about the domestic deployment is the fact that sometimes for weeks in a row you don't get to see your family or friends," said one soldier, who spoke on the condition of anonymity because he was not authorized to speak publicly.
In a sign of the degree to which Belgian war-fighting abilities had atrophied even before the deployment, the army had to borrow military-grade bulletproof vests from the U.S. Army because their own were too old. Belgian officials say they returned the last of them this summer after buying new ones.
Leaders also say they are starting to resolve an ammunition shortage. Thys, the commander of the Belgian land forces, said that every year the army needed about $32 million worth of ammunition. Until recently, it was spending $18 million.
And they plan to boost defense spending from its current level, which is less than half of what is recommended by NATO guidelines. NATO leaders have welcomed their efforts, but say that the spending laggards still need to do more. Belgium is the second-lowest defense spender in NATO, after tiny Luxembourg, when measured in proportion with the size of its economy.
"European allies should invest more in defense not only to please the United States, but they should invest more in defense because it is in their own interests," NATO Secretary General Jens Stoltenberg said this year as he announced defense spending increases across alliance nations.
Belgian defense leaders point to military deployments in Mali, Lithuania, Afghanistan and elsewhere as evidence that their nation is still active in the world.
Larger militaries have also felt the burden when soldiers have been sent into the streets.
"The number of missions that fall to our armies both in France and around the world has not been so high since the end of the Algerian War" in 1962, wrote French Gen. Pierre de Villiers in a memoir released last month. De Villiers was the commander of France's armed forces until he resigned in July following a dispute with French President Emmanuel Macron about military spending.
"The French Army is now in a real state of overheating, having to carry out so many missions with limited means," de Villiers wrote.
The consequences can be dangerous, retired French Gen. Vincent Desportes said.
"The guys underneath the Eiffel Tower are trained for what they do, individually. But if we are faced with a big situation globally, then we will not be ready because we are not trained enough," he said.
Annabell Van den Berghe contributed to this report.