The extremely challenging nature of warfare with China and Russia — should it ever come to that — is redefining how the Navy commands and controls its forces globally.

To that end, the new Large Scale Exercise 2021, running Aug. 3 to Monday, and testing cutting-edge technology linking Navy and Marine Corps sea, air, land, space and cyber assets, includes the deployment of the 3rd Fleet headquarters from San Diego to Pearl Harbor.

The series of 13 tents surrounded by razor wire that make up the “expeditionary maritime operations center” simulates a possible Western Pacific location during combat operations.

The 3rd Fleet has joined multiple other U.S. Navy fleets worldwide in contributing assets for the exercise ranging from aircraft carriers to submarines, with over 50 virtual units also involved.

From that series of tents near Hospital Point — populated by staff working on laptops — 3rd Fleet controls more than a dozen ships and submarines and Marine expeditionary forces in support of the exercise while continuing its usual job of leading naval forces in the Eastern Pacific from the West Coast to the international date line.

LSE 2021 “at its core is leveraging integrated fighting power of multiple naval forces to share sensors, weapons and platforms,” Rear Adm. Dan Martin, commander of Carrier Strike Group 1, which leads the Carl Vinson Carrier Strike Group, said in a Navy release. “Contemporary naval doctrine demands a shift of focus from the individual carrier strike group to a fleet-centric approach.”

The Large Scale Exercise overall seeks to synchronize five fleets and three Marine expeditionary forces across 17 time zones in a what-if scenario involving the Navy combating Russia and China simultaneously.

The Carl Vinson Strike Group deployed from San Diego and arrived in the Hawaiian Islands operating area Sunday and already took part in the exercise with a “long-range maritime strike” event, the Navy said.

The Pearl Harbor-based submarine USS Chicago recently onloaded Harpoon anti-ship missiles for the drills.

As far west as Guam, as part of LSE 2021, the 1st Marine Logistics Group provided supplies to sustain mobile, low-signature forces in what someday could be a combat zone.

Vice Adm. Steve Koehler, who commands the 3rd Fleet, told reporters Monday at Pearl Harbor that in his 35 years in the Navy, “this is a first of a kind where we are bringing all of the naval forces together, synchronized across the whole Navy.” He added that it is a “massive undertaking.”

The 6th Fleet, headquartered in Naples, Italy, said LSE 2021 is the first naval and amphibious large-scale exercise conducted since the Ocean Venture NATO exercises launched in 1981 during the Cold War.

Retired Navy Capt. Carl Schuster, a former director of operations at U.S. Pacific Command’s Joint Intelligence Center, said theater exercises are traditionally focused on one theater, and when that theater says it needs something, it almost always is available.

“But what happens when multiple theaters are competing for the same limited resources and strategic reserves?” he said. “That involves some very difficult and serious strategic thinking and coordination. What should we solve first, and where do we just hold on until that resource is available? We have not faced that kind of difficult decision-making process since World War II.”

To deter China, the Navy concluded that it needs greatly networked forces, a broad distribution of weapons with increased range and speed, a manned and unmanned fleet, and more mobility, stealth and deception.

The Marines plan to conduct fast-moving island-­hopping operations with smaller forces firing missiles to sink enemy ships at sea and then moving before being targeted themselves.

LSE 2021 is part of Large Scale Global Exercise 21, which has participation from other nations. U.S. Indo-Pacific Command on Oahu is running Large Scale Global Exercise incorporating Army, Navy, Air Force and Marine Corps forces alongside elements from the United Kingdom, Australia and Japan.

That exercise, running Aug. 2-27, “is a proof of concept global command and control pilot exercise with a regional focus,” Pentagon press secretary John Kirby said Monday.

“LSGE ’21 is an all-domain exercise across the Indo- Pacific in air, land and sea, field training, cyber and space operations, and special operations activities and logistics,” Kirby said. “It’s going to improve our interoperability, it’s going to strengthen our alliances and partnerships. And it offers a complex and challenging multinational environment for forces to hone their skills.”