China and Japan are building forces to fight it out on Pacific islands — here's how they stack up

• China has increasingly contentious relations with its neighbors, particularly Japan, with which Beijing has disputes over several islands in the East China Sea.
• While the risk of conflict is low, any clash between them would require forces that can approach, capture, and defend islands, and both are building military units to do just that.

Military success in the Pacific has always relied on two things: naval strength and amphibious capabilities. Bitter fighting between the Allies and Japan across the region's seas and islands during World War II made this abundantly clear.

China has carefully studied history, and its rapid increase in military might is now changing the balance of power in the world's largest ocean. That makes many of China's neighbors nervous — and one is responding in kind: Japan.

A well-equipped marine corps

Even amid China's overall military growth, the expansion of People's Liberation Army Navy (PLAN) and its Marine Corps (PLANMC) has been striking.

In the last three years, the PLANMC has grown from 10,000 marines to between 28,000 and 35,000 and has plans to eventually reach a total of 100,000.

After briefly forming and disbanding in the 1950s, the PLANMC was reestablished in 1979 and, like the PLAN, soon began receiving significant investment.

Today, the PLANMC has seven brigades and is present wherever the PLAN operates. Each brigade is heavily armed, including a minimum of two infantry battalions, an armored regiment, a howitzer battalion, a missile battalion, and a special forces amphibious reconnaissance battalion.

Particularly impressive are the PLANMC's armored amphibious vehicles. These include the ZBD-05 — which is actually faster on water and better armed than its Western counterpart, which Japan uses — and even a self-propelled howitzer, the PLZ-07.

The US Defense Intelligence Agency in 2019 called the PLANMC "a fully amphibious force capable of conducting amphibious assault operations using combined-arms tactics and multiple avenues of approach."

The PLANMC is "the most capable amphibious force of any South China Sea claimant," the agency said. This is due in large part to the strength of the PLAN, which is the world's largest navy with well over 300 vessels.

China is building ships faster than almost all of its competitors. According to a US Office of Naval Intelligence report, their "design and material quality is in many cases comparable to [US Navy] ships, and China is quickly closing the gap in any areas of deficiency."

This is certainly true of vessels used for amphibious operations.

The PLAN has long maintained a fleet of landing ships to carry tanks, troops, and equipment. That fleet has been bolstered by new, modern amphibious ships similar to those used by the British, French, and US navies.

Since 2006, the PLAN has acquired six Type-071 amphibious transport docks with at least one more on the way. These ships differ from previous landing ships in that they can carry hundreds of troops, multiple armored amphibious vehicles, and up to four air-cushioned landing craft (LCAC). It can also carry four or more transport helicopters, such as the Z-18, for air-assault missions.

In just over a year China has built two Type-075 amphibious assault ships — essentially small aircraft carriers that can carry 900 troops, multiple LCACs and armored vehicles, and up to 30 helicopters. China is building a third Type-075 ship and may even design a follow-on class to carry drones and jets.

The PLA's ground forces also have entire brigades dedicated to amphibious operations that would support the PLANMC.

Japan's first marine unit since WWII

While Japan has a more solid naval infantry tradition, its pacifist constitution limits it to defensive capabilities, prohibiting it from having a marine corps in the traditional sense.

But the rising threat Japan sees in China has forced it to think about how to handle a potential conflict with its massive mainland neighbor.

The Japanese are particularly worried about an invasion of their southern home islands — especially the Ryukyu Islands, which stretch from Kyushu to Taiwan. With most of those islands lacking a large military presence, Japan found that it would need the be able to rapidly deploy reinforcements.

This is a major shift from Japan's longtime focus on using armor and artillery to respond to a potential Soviet invasion from the north, Dr. Zack Cooper, a research fellow at the American Enterprise Institute, told Insider.

"Now they're having to actually turn 180 degrees [to] where armor and artillery aren't very useful and figure out how to get down to these islands in the south to deal with China," Cooper said.

As a result, Japan turned the small amphibious unit from its Western Army into an entirely new unit, the Amphibious Rapid Deployment Brigade, created in 2018.

It's Japan's first marine unit since World War II and now has about 3,000 troops. The ARDB is equipped with US-made AAV-7 amphibious assault vehicles and the Komatsu light armored vehicle. Japan also plans on acquiring up to 17 MV-22 Ospreys for transportation as well as a number of LCACs.

The brigade is modeled on and trains extensively with the US Marine Corps, giving it access to some of the most advanced training doctrine and methods available.

It is also supported by Japanese Maritime Self-Defense Force ships — particularly its two types of helicopter carriers, some of which will soon carry F-35B jets.

Different forces with different missions

The ARDB is nowhere near as strong as the PLANMC, but they aren't meant to do the same thing.

"The missions are very different," Cooper said. "What the Japanese are trying to do is protect their southwestern islands. The Japanese effort is a pretty limited amphibious capability much more focused on being able to resupply and reinforce existing forces on Japanese territory."

The ARDB, then, is meant to be a purely defensive force that would be just one part of Japan's response to an attack on its territory.

"It's a small force by design," Timothy Heath, a senior international and defense researcher at the Rand Corporation think tank, told Insider. "It's not designed to do something like seize a huge territory like Taiwan. It's designed to fight on the Senkaku Islands."

China, on the other hand, is trying to create an all-encompassing amphibious force with the capability to land and overcome entrenched enemy positions.

While the main target has always been Taiwan and the South China Sea, the PLAN and PLANMC are beginning to spread out to areas that are important to China's economic interests — namely the Indian Ocean and Middle East, including to Djibouti, the site of China's only overseas military base.

"Those are all areas that sorely need greater Chinese security or even military protection for some high-dollar investments," Heath said.

Potential for conflict

But Japan still has plenty to worry about. It has a number of maritime disputes with China, chief among them the Senkaku Islands, which China calls the Diaoyu Islands.

In a conflict, the PLANMC would likely try to seize Japanese-held islands like the Senkakus. The Japanese Self-Defense Force would send air and naval forces to stop them.

The ARDB would play a vital role as the first ground troops to reinforce or retake Japanese territory. Japan would also have help from the US, which is obliged by treaty to come to Japan's defense.

Amphibious operations will be vital in any conflict between China and Japan, but taking islands is just one part of it. Victory requires holding them against an enemy with modern and growing air, naval, and missile units.

"It's not hard for China or Japan to send a few hundred troops to land on the Senkakus and put up a flag and say, 'We conquered it,'" Heath said. "The real challenge is keeping them there alive."