President Donald Trump and North Korean leader Kim Jong Un are in place ahead of their second summit on Wednesday to address perhaps the world’s biggest security challenge.
Mr Kim’s pursuit of a nuclear programme that stands on the verge of viably threatening targets around the planet will be central to discussions in Vietnam that will build on last year’s encounter in Singapore.
Mr Trump arrived late on Tuesday in Air Force One after a long flight that included refuelling stops in the UK and Qatar.
He waved from the stairs of the presidential plane, then shook hands with dignitaries and walked along a red carpet to his motorcade.
Mr Kim arrived in Hanoi earlier and spent the day travelling around the Vietnamese capital in his armoured limousine, his squad of bodyguards in tow as he visited the North Korean Embassy, with hundreds of visiting journalists and thousands of local citizens following in his wake.
He took a train through southern China and then travelled to Hanoi by car from a Vietnamese border town.
The two leaders are slated to meet over two days, first at dinner on Wednesday followed by meetings on Thursday.
They first met last June in Singapore, a summit that was long on historic pageantry but short in any enforceable agreements for North Korea to give up its nuclear arsenal.
Mr Trump has praised Pyongyang for ceasing middle tests and has appeared to ease up on demanding a timeline for disarmament.
Mr Kim is expected to ask for relief from crushing US sanctions.
But before the summit began, Mr Kim took some time to venture out of his locked-down hotel and check out parts of Hanoi, including his nation’s embassy, where a loud cheer went up as he entered the compound.
Soldiers, police and international journalists thronged the streets outside Hanoi’s Melia Hotel where Mr Kim is staying, and hundreds of eager citizens stood behind barricades hoping to see the North Korean leader.
As Vietnamese, North Korean and US flags fluttered in a cold drizzle, dozens of cameras flashed and some citizens screamed and used their mobile phones to capture Mr Kim’s rock-star-like arrival.
“I like him,” local resident Van Dang Luu, who works at a nearby bank, said of Mr Kim.
“He is very young and he is very interesting. And he is very powerful,” she said.
“Trump is not young, but I think he is very powerful.”
Vietnam’s authoritarian leaders set up a huge security apparatus to welcome Mr Kim, shutting long stretches of road and locking down swaths of the bustling capital city.
Earlier in the morning, Mr Kim, grinning broadly and waving, stepped off his armoured train at the end of a long ride that started in Pyongyang and wound through China to the Vietnamese border.
He shook hands with officials as Vietnamese troops in crisp, white uniforms and black boots stood at attention on a red carpet at the Dong Dang railway station on the China-Vietnam border.
Hours ahead of his border crossing, footage from Japanese TV network TBS showed Mr Kim taking a pre-dawn smoke break at a railway station in China, a woman who appeared to be his sister, Kim Yo Jong, holding a crystal ashtray at the ready.
Although many experts are sceptical Mr Kim will give up the nuclear weapons he likely sees as his best guarantee of continued rule, there was a palpable, carnival-like excitement among many in Hanoi as the final preparations were made for the meeting.
There were also huge traffic jams in the already congested streets.
Vietnam is eager to show off its huge economic and development improvements since the destruction of the Vietnam War, but the country also tolerates no dissent and is able to provide the kind of firm hand not allowed by more democratic potential hosts.
“I really hope to catch a glimpse of Kim Jong Un. He is an interesting man. And he rarely travels anywhere so it would be great to see him here,” said Nguyen Trong Toan, a retired teacher who was waiting by the side of the street on Kim’s expected travel route.
There are high expectations for the Hanoi summit after a vague declaration at the first meeting in June in Singapore that disappointed many.
Mr Trump, via Twitter, has worked to temper those expectations, predicting before leaving for Hanoi a “continuation of the progress” made in Singapore but adding a tantalising nod to “denuclearisation?”
He also said that Mr Kim knows that “without nuclear weapons, his country could fast become one of the great economic powers anywhere in the world”.
North Korea has spent decades, at great political and economic sacrifice, building its nuclear programme, and there is widespread scepticism among experts that it will give away that programme cheaply.