TWENTYNINE PALMS, Calif. — Sitting around a plastic folding table in a dusty tent, a half-dozen officers of the Hawaii-based 3rd Marine Littoral Regiment took a very short break from days of fighting on little to no sleep.

The war, they said, was going well.

The unit, newly created and innovative in nature, was facing its toughest test yet — a 10-day mock battle across Southern California, where a series of military bases played the role of an island chain. Although outnumbered by the regiment it was fighting, the team from Hawaii had an edge.

The team was built to fight on islands and along coastal shorelines, the “littoral region” in military parlance. It had also been given special equipment and the freedom to innovate, developing new tactics to figure out one of the service’s highest priorities: how to fight a war against Chinese forces in their own backyard, and win.

Although far from the ocean, the base at Twentynine Palms offers about 1,200 square miles to train, more than all of the Marine Corps’ other training bases combined. Days ago, the two sides were dropped off here about 12 miles from each other. Then it was time to fight.

No live ammunition was used, but that was essentially the only rule. Evaluators alongside them graded everything they did, assessing hits and misses and pulling troops out of the action when they had been “killed.”

Over the next two years, the new unit will have a relentless schedule, with about four or five times as many exercises as most infantry regiments. Its next big test will be in the Philippines in April.

“We have to unlearn the way that we were trained,” said Gen. David H. Berger, the service’s top general.

In the end, the 3rd Marine Littoral Regiment remained in control of its terrain and had fended off its opponents — which it considered a victory.

All of the work done so far in Hawaii and California will soon benefit a new unit, the 12th Marine Littoral Regiment, which military leaders have said will be established in Okinawa in 2025.

That unit, based in Japan, will be the closest to the island chains stretching many thousands of miles across the Pacific, which could become battlefields once again.

This article originally appeared in The New York Times.