Members of the storied foreign-fighter unit huddle on a military base in southern France, located hundreds of kilometres from Paris' cafe-lined streets where they will deploy in just a few weeks.

"There's no Eiffel Tower, but we're in Paris," says Lieutenant Antoine to the troops gathered around him, who, like all legionnaires, had to change his name upon joining.

Metal barracks stand in today for the gleaming arenas these soldiers will soon be scouring for "suspicious objects" with the help of dogs and drones.

The Foreign Legion, a corps of some 10,000 soldiers founded nearly 195 years ago, is the only French army unit in which foreign nationals can enlist.

They can apply for French nationality after several years of service, or sooner if they distinguish themselves in battle in places like Niger, where they fought against an Islamist insurgency.

But this summer, they are heading to the French capital, where the soldiers will work alongside police as part of the country's heightened security posture during the Games.

The Olympics are set to take place from July 26-August 11 followed by the Paralympics from August 28-September 8.

-'A lot of factors'-

Before the search exercise can start, Lieutenant Antoine wants to ensure the legionnaires -- whose French is often broken -- understand how the operation will be carried out.

"What is a K-9 unit?" he asks in French.

One legionnaire has the correct answer -- a police dog -- but in his native Nepalese, not French.

The language barrier is nothing new for this unit, where some 30 nationalities work side-by-side, but joining forces with police and private security unaccustomed to the legion's multicultural nature will pose a challenge.

To get them ready, one soldier plays the role of an uncommunicative security guard, but even so the legionnaires quickly find a bottle filled with a suspicious substance, and a dog sniffs out a 500-gram plastic object hidden under the floorboards.

Pleased with the "fairly rapid detection", Captain Aymeric told AFP his men are ready to join the some 20,000 military personnel deployed for the Olympics.

But Lieutenant Hugo, who like all soldiers can give only his first name, says Paris presents different challenges, including the "complexity and density of the urban environment".

During previous deployments to the Sahel, soldiers might have had an entire day to search a village but in Paris they will be searching huge venues with a time limit.

In late January, the French government slashed the crowd size for the opening ceremony this July in half from 600,000 to around 300,000, amid security and organisational concerns.

There are "a lot of factors, a lot of players," the lieutenant said.

-'Makes me proud'-

Originally from Nepal and enlisted in the FFL in 2018, Sergeant "Ganesh" says he is aware of how important the legion's role is this summer.

"The Olympics motivate me even more," said the former student from Luxembourg, adding, "working for France makes me proud".

Patriotism is not a requirement for the legion, whose motto, "Honour and Fidelity", puts solidarity between brothers-in-arms over national feeling.

There are very few conditions for those looking to join: applicants must not have convictions for serious crimes like murder or paedophilia, be combat-ready, willing to serve for five years, and learn French.

Since the start of the war in Ukraine, Belarusians and Russians can no longer join.

As for the rest, the French army gives leeway for the sometimes chequered pasts' of its legionnaires.

For many, the decision to join the foreign legion is made by those looking to start a "second or third life", said Captain Aymeric.

"What interests me is not what they did before," he said, "but what they're ready to do for us".