Some time in November 1947, workers in Osaka finished scrapping the aircraft carrier Katsuragi. Imperial Japan’s fleet of large flattops had given the US Navy a hard fight, starting with their devastating raid on Pearl Harbor in December 1941. Now the last Japanese wartime carrier was gone.

Seventy-four years later in October 2021, a US Marine Corps F-35B Lightning II stealth fighter landed on Izumo, a former amphibious assault ship that the Japanese navy had recently converted into the fleet’s first modern flattop.

Japan is back in the carrier club. And the implications, for the whole Asia-Pacific region but especially for Taiwan, are profound. A more powerful Japanese fleet, sailing under its own stealth-jet air cover, could play a crucial role in defending the region’s democracies from an increasingly aggressive authoritarian China.

The 27,000-ton Izumo and her sister Kaga aren’t big ships compared to the US Navy’s 11 supercarriers, each of which displaces around 100,000 tons. The Chinese navy’s own carriers – two in service, another building – are much heavier than Japanese carriers, though not on the scale of US ships.

But the Japanese flattops’ small size belies their capability. They can each accommodate a squadron of 14 vertical-landing F-35Bs, 42 of which the Japanese air force is buying specifically for operations from the carriers. A single-seat, radar-evading F-35B can range 500 miles with tons of precision missiles and bombs loaded in its weapons bay.

The US Navy is so optimistic about the F-35B’s potential that it’s been modifying its own amphibious assault ships – 10 vessels each displacing 40,000 tons – to operate a dozen or more Marine F-35Bs apiece. During a major war, these “Lightning carriers” could complement the supercarriers, each of which embarks around 70 aircraft.

“While the amphibious assault ship will never replace the aircraft carrier, it can be complementary, if employed in imaginative ways,” the Marine Corps stated. “A Lightning carrier, taking full advantage of the amphibious assault ship as a sea base, can provide the naval and joint force with significant access, [intelligence] collection and strike capabilities.”

Restoring its long-abandoned carrier capability transforms the Japanese fleet. Where before Japan’s dozens of destroyers and frigates – themselves a significant force – would need to stay within range of land-based air support or sail close to American flattops, now they can range freely across the Pacific Ocean under the protection of their own carrier-based F-35s.

This might matter most in a possible Chinese invasion of Taiwan. As the Chinese fleet has grown more powerful in recent decades, the odds of a Chinese victory over Taiwan have improved.

But China’s rise as a naval power has provoked an equal response from Japan. In 2023, Tokyo budgeted a record $53 billion for defense, a sum that helped pay for the two carrier conversions plus the F-35Bs and their new bases.

The government in Tokyo has spent years loosening the constitutional constraints on its military operations. And a few years ago, defense officials began implying the Japan Self-Defense Forces would extend their defensive mandate to Taiwan. “We have to protect Taiwan, as a democratic country,” deputy defense minister Yasuhide Nakayama said in 2021.

Today American analysts assume Japan would join the United States and other Pacific democracies in defending Taiwan from a Chinese attack. The addition of Japanese ships and planes could be decisive.

At least, that’s what the Washington DC-based Center for Strategic and International Studies found early this year when its analysts gamed out a Chinese invasion of Taiwan. In the likeliest invasion scenarios, “US submarines, bombers and fighter/attack aircraft, often reinforced by Japan Self-Defense Forces, rapidly cripple the Chinese amphibious fleet,” CSIS concluded.

But CSIS set its war game in 2026. If China attacks this year or next, the Japanese fleet might not be ready for a major fight. American F-35s have landed on Izumo, giving the vessel’s crew a preview of their own flight operations. But the Japanese air force won’t deploy its first F-35Bs until 2024. And Kaga won’t be ready for fixed-wing aircraft until 2027.

That’s a long time to wait in a region that’s increasingly unstable. Sensing that tension, the Japanese fleet has partnered up with the US Marine Corps – and the Italian navy, too. Marine and Italian F-35Bs could embark on Japanese carriers until Japanese F-35Bs are available.

If different countries’ militaries mixing and matching warships and warplanes seems outrageous, consider that the US Marines and the Royal Navy have already done it. When the British carrier HMS Queen Elizabeth deployed in 2021, she had 10 USMC F-35Bs aboard alongside eight British F-35Bs, operated by a joint force of RAF and Royal Navy personnel.