If a summit between Donald Trump and Kim Jong Un takes place in May, it will count as one of the most remarkable and unexpected pieces of theatre in diplomatic history.
Any substantive peace agreement that comes out of it would represent an extraordinary achievement. The Korean war never formally ended and the threat of a new devastating conflict has hung over the peninsula for decades.
Peace talks are a prize on an epic scale, but so are the risks. Both leaders view the provisional agreement to meet as a personal triumph born of resolve. If each reckons he has the other over a barrel, there will be little room for compromise if and when they meet.
The South Korean messengers who conveyed Kim's invitation also went out of their way to tie the surprise development tightly to the US President's leadership qualities.
Having invested so much personal capital in the meetings, there is a significant danger of a backlash from either or both men if they do not get their way under the glare of international attention.
Both leaders say they want the denuclearisation of the Korean peninsula, but historically their governments have interpreted that to mean quite different things: Washington sees it in terms of North Korean unilateral disarmament; Pyongyang envisions an end to the "hostile policies" of the US and the formal removal of the nuclear deterrent umbrella that has sheltered South Korea from its northern neighbour.
There is no guarantee of the summit actually taking place. Kim did not put his invitation down on paper. It was relayed orally by the South Korean national security chief, Chung Eui Yong.
Since Kim met Chung and his delegation on Monday in Pyongyang, the North has remained silent on the contents of the offer and could seek to move the goalposts in the run-up to the high-stakes meeting.
Trump could not contain his excitement at Friday's developments. He appeared unannounced at the White House briefing room to tip off journalists about Chung's planned press statement. He told one reporter he hoped to garner the credit for the breakthrough.
He seemed unaware that Pyongyang had been seeking a one-on-one meeting with a US president since the 1990s at least. In securing agreement, Kim can claim an achievement that eluded his father and grandfather — being treated in the eyes of the world as an equal by the most powerful man on earth.
"To be clear — we need to talk to North Korea," argued Jeffrey Lewis, the director of the East Asia Nonproliferation Programme at the Middlebury institute of international studies at Monterey.
"But Kim is not inviting Trump so that he can surrender North Korea's weapons. Kim is inviting Trump to demonstrate that his investment in nuclear and missile capabilities has forced the United States to treat him as an equal."
The timing has also been benign. The election of a pro-engagement president in South Korea has been followed by Kim's declaration at the start of this year that his regime had attained its goal of building an arsenal of nuclear missiles. The Pyongyang regime now sees itself entering negotiations from a position of strength as a nuclear power.
The White House narrative is entirely different. It portrays North Korea as cowed into talks by Trump's determination and the unprecedented international sanctions regime that has been imposed since last September.
However, any expectation Trump might have that Kim will trade his nuclear weapons for sanctions relief may be ill-conceived. Few observers believe the North Korean leader will bargain away lightly what he sees as a guarantee of his dynastic regime's survival.