Three decades ago, the world was on the brink of a nuclear showdown - until Jimmy Carter showed up in North Korea.

In June 1994, the former US president arrived for talks in Pyongyang with then leader Kim Il-sung. It was unprecedented, marking the first time a former or sitting US president had visited.

But it was also an extraordinary act of personal intervention, one which many believe narrowly averted a war between the US and North Korea that could have cost millions of lives. And it led to a period of greater engagement between Pyongyang and the West.

All this may not have happened if not for a set of diplomatic chess moves by Carter, who died aged 100 on 29 December.

"Kim Il-sung and Bill Clinton were stumbling into a conflict, and Carter leapt into the breach, successfully finding a path for negotiated resolution of the standoff," North Korean expert John Delury, of Yonsei University, told the BBC.

In early 1994, tensions were running high between Washington and Pyongyang, as officials tried to negotiate an end to North Korea's nuclear programme.

US intelligence agencies suspected that despite ongoing talks, North Korea may have secretly developed nuclear weapons.

Then, in a startling announcement, North Korea said it had begun withdrawing thousands of fuel rods from its Yongbyon nuclear reactor for reprocessing. This violated an earlier agreement with the US under which such a move required the presence of inspectors from the International Atomic Energy Agency (IAEA) nuclear watchdog.

North Korea also announced it would withdraw from the IAEA.

American suspicion spiked as Washington believed Pyongyang was preparing a weapon, and US officials broke off negotiations. Washington began preparing several retaliatory measures, including initiating UN sanctions and reinforcing troops in South Korea.

In subsequent interviews, US officials revealed they also contemplated dropping a bomb or shooting a missile at Yongbyon - a move which they knew would have likely resulted in war on the Korean peninsula and the destruction of the South's capital, Seoul.

It was in this febrile atmosphere that Carter made his move.

For years, he had been quietly wooed by Kim Il-sung, who had sent him personal entreaties to visit Pyongyang. In June 1994, upon hearing Washington's military plans, and following discussions with his contacts in the US government and China - North Korea's main ally - Carter decided to finally accept Kim's invitation.

"I think we were on the verge of war," he told the US public broadcaster PBS years later. "It might very well have been a second Korean War, within which a million people or so could have been killed, and a continuation of the production of nuclear fissile material… if we hadn't had a war."

Carter's visit was marked by skillful diplomatic footwork - and brinkmanship.

First, Carter had to test Kim's sincerity. He made a series of requests, all of which were agreed to, except the last: Carter wanted to travel to........

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