What would happen if a missile from North Korea actually hit Japan?

Experts say Donald Trump would be forced to instanty launch a strike as part of Washington’s obligation to the treaty - triggering an all-out world war

The US would have been forced to immediately attack North Korea had the missile Pyongyang fired over Japan hit its territory rather than landing in the sea off its coast, experts say.

Japan is a long-standing Nato partner which means a strike by a foreign power on its soil is deemed as an attack on all the countries in the alliance, meaning member nations are obliged to react.

Tokyo would have declared war against Pyongyang regardless of whether the "reckless act" by Kim Jong-un had not intended to directly target the island nation, analysts say.

The United States, which has the biggest military presence of the member states in Asia, would have launched a counter-attack either with a nuclear missile or other strike.

And that would have plunged the world into all-out war, with fears that China could wade into the conflict and defend North Korea.

The threat of global warfare came when Pyongyang fired a missile, thought to be a new Hwasong-12, which torpedoed into waters off Japan’s northern island of Hokkaido.

Kim Jong-un fired the intermediate-range weapon despite the threat by US president Donald Trump that North Korea would feel the “fire and fury” if it launched further missiles towards Japan.

“It’s extremely serious. Most wars happen by accident, not by design, and if these missiles had landed on Japan there would have undoubtedly been war this morning,” Professor Anthony Glees, a security expert with the University of Buckingham, told The Independent.

“I think Japan would have been forced to declare war on North Korea. It would have been seen as an attack on Japan.

“Japan is a Nato partner. Retaliation is obligatory, it is not a choice. We know the US is a guarantor of Japan’s security. Even if they retaliated with conventional weapons against North Korea, it would then escalate straight away.

“It was a totally, reckless, dangerous act by North Korea. The whole world is lucky that these weapons did not kill anybody in Japan.”

Adam Mount, a senior fellow at the Washington-based Center for American Progress, told CNN that North Korea launched the missile to reinforce the message that Pyongyang can deter any US-led regime change.

“They cross line after line in an effort to say this is the new reality and you should accept it and go easy on us,” Mr Mount said. “I think that's a pretty unambiguous signal that they're no longer going to be restrained by the United States.”

The Japanese prime minister Shinzo Abe denounced the launch as an “unprecedented and grave threat” to the country’s security. In a 40-minute phone call with Mr Trump, the pair agreed to call for an emergency meeting of the UN security council to discuss the situation.

Mr Trump said the US was “100% with Japan” and repeated his strong commitment to the defence of Japan, Mr Abe said shortly after the call.

“The outrageous act of firing a missile over our country is an unprecedented, serious and grave threat and greatly damages regional peace and security,” Mr Abe told reporters in Tokyo, adding that his government had protested to Pyongyang through the Japanese embassy in Beijing.

The missile was the third fired by North Korea to have passed over Japanese territory. The first was in 1998 and the second in 2009, although Pyongyang claims they were satellites.