President Donald Trump's announcement that the US would suspend military exercises with South Korea left one of their most experienced military leaders "speechless".
After the summit, Mr Trump said the military exercises would cease as a concession to Kim Jong-un, after the North's leader re-committed to the "complete" denuclearisation of the Peninsula.
Retired lieutenant-general In-Bum Chun, a three-star general who served in the Republic of Korea Army for nearly 40 years, said he would have expected that kind of an announcement to come at a later phase of negotiations with North Korea.
"Something that would have been thoroughly consulted with Korea, and probably with Japan. So it came as a bit of a surprise," he said.
General Chun said one thing that was "unclear about this exercise" was whether it was simply to give North Koreans assurances that South Korea was sincere about its peaceful motives.
"One of the things that President Trump mentioned first was the cost of this, so maybe this is just to get a higher ground for the cost sharing negotiations," he said.
"But again I just want to emphasise that the exercise is not provocative from our perspective, it's a purely defensive exercise to maintain readiness."
Once the details are released about the summit between the United States and the DPRK, General Chun said those issues would need to be discussed.
"I'm glad that President Trump finds Kim Jung-un a nice person and smart, but I think the businessman Donald Trump will soon remember that this is a shrewd negotiator and a person who is not reluctant to use bloodthirsty measures," he said.
"So he better remember he is a killer shark here.
"The last time the US pulled out of Korea war broke out — it cost the Americans 50,000 lives, not to mention the destabilising factor to North-East Asia.
"I think that's one bit of history that's important for the United States and all regional partners to remember.
"So talking about withdrawal of US forces is something that needs to be really thought through."
Interviewed on Sean Hannity's program on Fox News in the US, Mr Trump said the denuclearisation process was "moving rapidly".
"I just think that we are going to start the process of denuclearisation of North Korea, and I believe that [Kim Jong-un] going back and will start it virtually immediately," Mr Trump said.
"And he's already indicated that and you look at what he's done."
General Chun said from his conversations with experts in the field, the estimates they gave would be that it would take from five to 15 years for complete denuclearisation.
"I think from their advice it's going to be a long haul," he said.
"And that's where one of the pitfalls and challenges we're facing, because we're going to need consistencies to ensure that North Korea denuclearises — it's not going to be easy."
'Do not be fooled by Trump'
General Chun warned North Korea to remember who they were dealing with.
"Mr Trump is a shrewd negotiator, just because he said one thing doesn't mean that he's going to do that," he said.
"We've seen it happen to other friends of Mr Trump, it should be a good warning to Kim Jong-un as well."
If there comes a point that Mr Trump believes that he is in some way being manipulated, then Kim Jong-un should be wary of the president.
"I would say to Chairman Kim, do not be fooled by the casual nature of Americans — or even the South Koreans," he said.
"Kim might think that he can get away with anything that he wants, so I warn him that just because the Americans and the South Koreans seem casual and open, doesn't mean that they're stupid."
'I cannot be optimistic' over 'deja vu' summit
The current chief nuclear envoy to the Six-Party Talks for the Republic of Korea, Wi Sung-lac, said the summit had mixed results, but it was all "deja vu."
"It represented a kind of a big achievement in terms of political symbolism," he said.
"But in terms of substance, the result is pretty much limited."
Mr Wi said a careful review of the joint statement revealed "not much advances in the area of denuclearisation."
"Based on previous experiences, I cannot be optimistic," he said.
Mr Wi said previous agreements between the two countries failed because of a lack of confidence between them.
"They do not have trust on each other. So whenever some events happens, the suspicious mind prevails," he said.
When asked how he thought everything would look 12 months down the road, Mr Wi was not optimistic.
"Follow-up negotiation between Pyongyang and Washington will not be easy, it will be the repetition of what we have seen before," he said.
"We will see a high level of symbolism, but a low level of substantive outcome."