TOKYO – Over nearly seven decades, Japan has relied on commitments from the United States, its most important ally, for protection in the event of an enemy attack.

Japan hosts the largest contingent of overseas American troops and regularly conducts drills with them.

It has purchased more American-made F-35 stealth fighter jets than any other country outside the US.

Yet now, as Russia’s invasion of Ukraine challenges long-held security assumptions and as threats from China and North Korea multiply, Japan is starting to rely more on itself, a shift that could quietly alter the balance of power in Asia.

The country’s governing party is pushing to increase Japan’s defence budget drastically, develop more military hardware domestically and redefine what it can do with those weapons under the pacifist Constitution in place since the end of World War II.

By asserting its own deterrent power, Japan – the world’s third-largest economy – could become less a military protectorate of the US and more an equal partner.

That could help fulfil the desire of US leaders for Japan to serve as a stronger military counter to China, as Beijing uses its rapidly improving armed forces to menace Taiwan and send ballistic missiles and coast guard ships into Japan’s territorial waters.

Japan must also confront a more bellicose North Korea, which has launched flurries of missiles – including one that flew over Japan’s northernmost island – in recent weeks, seemingly emboldened to expand its nuclear arsenal while the world grapples with the war in Ukraine. At a meeting of South-east Asian nations and their allies in Cambodia on the weekend, Japanese Prime Minister Fumio Kishida noted that Taiwan’s stability “directly impacts” regional security, and criticised Beijing for “intensifying” activities that threaten to violate Japan’s sovereignty in the East China Sea.

And in a meeting between Mr Kishida, US President Joe Biden and South Korea’s President Yoon Suk-yeol, the three leaders vowed to take “resolute steps” to denuclearise North Korea.

It is a delicate geopolitical moment that requires deft juggling.

While Japan wants to demonstrate that it is a potent military force in its own right, it does not want to antagonise China, an important trade partner, or spook neighbours in South-east Asia that want to avoid taking sides and might view Japan’s muscular security posture as a risk to regional stability.

But some defence experts say Japan must be more realistic about the limits of American protection, with Washington preoccupied by war in Europe and an erratic US political landscape in which changes of administration can lead to swift swings in policy.

“If we are in a crisis situation, will the US military comes to our rescue in all cases?” said Mr Shigeru Iwasaki, a retired general and chief of staff to the Japanese Air Self-Defence Force.

Ultimately, with Japan nearly surrounded by threats, its effort to become more self-sufficient is intended not to distance it from the US’ protective umbrella, but to ensure that Tokyo’s bond with Washington remains strong.

“We have to fortify our defences in order to fortify the alliance,” said Mr Ichiro Fujisaki, a former Japanese ambassador to the US.

“We can’t let the Americans do everything, and we have to do more on our own.”

A growing piece of Japan’s self-reliance is the development of domestically manufactured missiles that could be used to defend against foreign attacks or that might even be able to reach targets inside enemy territory.

The Defence Ministry has also started a project to build a new fighter jet and is testing hypersonic missile defence technology.

There are questions about whether Japan has the expertise to develop cutting-edge military hardware.

In 2021, less than 2 per cent of all government-sponsored research was allocated to defence in Japan, compared with close to half in the US and 10 per cent in France, according to data from the Organisation for Economic Cooperation and Development.

But last year, the Japanese government authorised record-high research and development spending within its overall defence budget, more than double the level of five years earlier.

This year, the Defence Ministry has made another record-setting request that includes a greater emphasis on domestic weapons development.

The governing Liberal Democratic Party has proposed that Japan increase its defence budget to 2 per cent of economic output over the next five years – up from about 1 per cent – a goal that would align with members of Nato.

The Cabinet of Mr Kishida will issue its official budget plan next month, and Parliament will vote on it early next year.

Until recently, the Japanese public baulked at any proposal to drastically change defence spending.

Now, as Russia’s invasion of Ukraine has triggered fears that China might seek to consolidate its authoritarian power and invade Taiwan – which lies less than 160km west of Japan’s southernmost islands – recent polls show that more than half of the Japanese public supports a significantly expanded defence budget.

Officials say Japan will continue to purchase US or other Western-made equipment.

Yet they say they need to procure more military hardware from Japanese manufacturers at a time when import orders can suffer delays or when spare parts are difficult to secure because of supply chain issues.

“If Japan only relies on American equipment, maintenance could be difficult,” said Mr Itsunori Onodera, chair of the Liberal Democratic Party’s Research Commission on Security and a former defence minister.

Mr Onodera said Japanese military officials had also become increasingly frustrated that US manufacturers lock down classified technology they sell to Japan.

As a result, he said, the Japanese military cannot adapt fighter jets or missile defence systems purchased from the US.

Japan began developing a new fighter jet two years ago.

It has spent more than 200 billion yen – about S$1937 billion – on the so-called F-X, which is being designed by Mitsubishi Heavy Industries, one of Japan’s oldest industrial conglomerates.

Japan’s Defence Ministry initially consulted US defence contractors about a potential partnership, Mr Onodera said.

But “the US said they don’t have a specific plan in place for a next-generation fighter jet”, he added.

Japan is in discussions with the British government about a collaboration between Mitsubishi Heavy and BAE Systems, Britain’s largest defence contractor.

One appeal of a British partnership is more open technology sharing, said Mr Tsutomu Date, an official in the aircraft project management division within Japan’s Defence Ministry.

BAE declined to comment.

Lieutenant-Colonel Martin Meiners, a US Department of Defence spokesman, said the US supported Japan’s “cooperation with like-minded allies and partners, including the United Kingdom”, adding that the US and Japan “are bolstering our defence cooperation in a number of promising areas”.

Still, by choosing a British partner, said professor of Japanese studies Christopher Hughes at the University of Warwick, Japan is “trying to somewhat hedge its bets and to retain some autonomy in its security ties”.

Some experts say Japan does not have the knowledge to develop a sophisticated fighter jet, and they suggest that the government is using defence spending to subsidise domestic manufacturers.

The F-X project is a “dream for the engineers”, said Mr Yoji Koda, a retired vice-admiral in Japan’s Maritime Self-Defence Force, but “to defend our country against an enemy threat and should war break out, we have to win. Our own indigenous developed fighters should be able to kill the enemy if necessary. Where is the guarantee?”

Analysts also question Japan’s decision to fund domestic development of a variety of missiles, including those that could attack enemy targets abroad.

In an interview in his office, Mr Onodera demonstrated the prospective capabilities of the new missiles being developed by Mitsubishi Heavy.

He pointed to a pair of business cards on the table in front of him: these represented Japan. About 60cm away, he set down a large mailing envelope: an unnamed enemy country. Two small plastic bottles of green tea stood in for Japanese and enemy ships or jets.

He brought the bottles lid to lid in the air above the table to demonstrate how a missile launched from Japan might hit an incoming missile.

Landing one of the tea bottles onto the envelope, he suggested another possibility: a Japanese missile might fly all the way to a target inside enemy territory.

Mr Onodera acknowledged that Japanese law was unclear on whether missiles could target sites inside another country.

Given that ambiguity, analysts question whether spending to develop missiles with extended ranges was a wise use of government money, especially as the rapidly ageing, debt-laden country faces questions about how to afford a big jump in defence spending.

Defence experts say more urgent spending is needed to build better shelters for existing aircraft, install communication and backup fuel lines, and shore up munitions stockpiles.

By protecting what Japan already has, said Mr Jeffrey Hornung, a senior political scientist at the Rand Corporation who specialises in Japanese security, “when a Chinese strike does come, their capabilities can survive an attack”. NYTIMES