In and on the water, French troops secure the River Seine for the Paris Olympics opening ceremony

PARIS — French soldiers and police are being deployed both in and along the River Seine to make it safe during the grandiose opening ceremony of the Paris Olympics, when thousands of athletes will sail down the river at sunset toward the Eiffel Tower.

The unprecedented decision to use a 6-kilometer (3.7-mile) stretch of the Seine as a spectacular stage for the July 26 ceremony in front of a 320,000-strong crowd has created a huge challenge for security services, who will need to ensure the safety of Olympians and spectators alike.

French authorities said 45,000 police officers and gendarmes are being deployed for the occasion, as well as 10,000 soldiers of the so-called Sentinelle military operation.

A specially-created battalion has been tasked to secure the embarkation zone for athletes located along Paris' eastern portion of the river. The battalion's mission includes the full protection of the area, the boats and the attendees, in close coordination with other security forces.

''This mission is complex and unprecedented,'' Lieutenant-Colonel Olivier, chief of operations of the battalion, said Wednesday. "It's complex because we're in an environment — the Parisian environment, the Seine — which is an urban environment ... with obvious vulnerabilities. The Seine is an area where there are a lot of activities.''

Former U.S. President Donald Trump's assassination attempt Saturday further raised awareness about the highly sensitive mission.

Paris has been the target of deadly terror attacks in the past decade, and the Seine flows through the heart of the city, surrounded by office and apartment buildings and used every day by barges and other ships.

''We were already on a very high level of security. So the attack on Donald Trump only reinforces our vigilance,'' Lieutenant-Colonel Olivier said.

Military officers requested to be identified by their first names only for reasons of security.

Specialized units have been mobilized for the operation that involves deployment of high-tech technology such as drones and sonars, as well as combat divers, boat intervention groups, patrols along the Seine and military dogs. Water barriers going from the riverbed to the surface have been installed to prevent any intrusions into protected area.

In addition, the battalion is using counter-drone systems and works in close coordination with the French Air Force, which secures the Paris skies, Lieutenant-Colonel Olivier said.

The military ''is ready to respond to any type of threat'' that may be underwater, on water, on land or in the air, Captain Quentin, who is commanding a company of the 13th Demi-Brigade of the Foreign Legion, said.

Troops aboard rapid boats ''are able to intervene at very short notice, to any type of threat, to cross the Seine in a matter of minutes and rapidly deploy for deterrence or to take action on site,'' he said.

A special anti-terrorism perimeter for the opening ceremony will start being implemented Thursday. Protected areas along the Seine have a special legal status, making them off-limits to the unauthorized public.

Staff Sergeant Sofiane, from the 132nd Canine Infantry Regiment, said his 3-year-old dog, Stimo, is trained to detect intruders and would alert him by barking.

In case of an intrusion the staff sergeant could order Stimo to attack and neutralize an intruder, either hitting the person with a very rigid muzzle or attacking without the muzzle.

With France soon to be in the world's spotlight, the Olympics security mission is a unique experience for the soldiers, and even a chance for some to discover Paris.

''They have the feeling that they are there for something special,'' Captain Quentin said. ''And they're all the more vigilant and ready for the occasion.''