One of the biggest Navy and Marine Corps training exercises launched Wednesday with Large Scale Exercise 2025, the third iteration of an all-of-Navy exercise that takes place across the world.

LSE 2025 includes six component commands, all seven numbered fleets, and sailors and Marines across 22 time zones, a Fleet Forces Command news release said. It is the only exercise that features the simultaneous operation of all 10 Fleet Maritime Operations Centers, according to the release.

LSE features live training and virtual simulations of scenarios intended to stress-test the Navy and Marine Corps without physically wearing down their materiel. Those taking part are doing so from bases and ships at sea.

The scale and complexity of the exercise is intended to mirror the challenges posed by strategic competitors.

“This isn’t just about scale — it’s about integration, synchronization and rehearsal for the full spectrum of conflict,” Vice Adm. John Gumbleton, the deputy commander of U.S. Fleet Forces Command, said in the release.

Gumbleton also said LSE 2025 will test the military’s ability to “execute contested logistics.”

The 2025 iteration of LSE is also the first to include allied forces, the release said. The previous iterations took place in 2023 and 2021.

Though the number of participants was not publicly stated, the previous version of the exercise included about 25,000 sailors and Marines.

LSE 2025 launches as two other major training exercises are underway: Talisman Sabre 2025, a bilateral U.S.-Australia exercise; and REFORPAC 2025, the Pacific Air Forces’ largest contingency response exercise. Both are still ongoing.