Gwangju, South Korea (CNN)Military drills on the Korean Peninsula are always a source of tension, but this year's Max Thunder exercises were on another level.
Did these US-South Korean military drills cause Kim's change of heart?
They're the drills North Korea called an "intentional military provocation" and cited as the reason for canceling inter-Korean talks. It was first sign of trouble ahead of the planned Singapore summit, which Donald Trump ultimately canceled, depriving Kim Jong Un of his first meeting with a US President.
Max Thunder is conducted annually by the US and South Korean air forces, which regard them as defensive, and necessary for training and maintaining the military alliance.
In North Korea, where memories of a brutal US bombing campaign during the Korean War are still fresh, the drills are viewed very differently. Pyongyang, and some outside observers, regard them as acts of aggression, implicit threats to the Kim regime.
CNN was among a small group of journalists given access to the drills: filming F16 fighter jets being loaded with heat-seeking and GPS guided missiles, and then targeting an imaginary aerial threat.
Footage of the drills was strictly embargoed until they concluded on Friday.
Staff Sgt. Joseph Pullins, who was evaluating the arming of the F16s, acknowledged that Max Thunder is not like a normal training exercise, not with North Korea mere miles away.
"I mean, we always know that you know there's a threat pretty close by," he said. "So, you just have to be ready to perform your job and be able to execute."
Col. David Shoemaker, the commander of the US 8th Fighter Wing who was overseeing this year's drills, said he was aware of the heightened tensions around the drills, but argued they were necessary.
"This is training that we need regardless of the political situation," he said. "It's training that has gone on for decades."
North Korea has complained for decades too, but this year was supposed to be different. A South Korean delegation which met with Kim said the North Korean leader appeared to suggest he understood the need for them and wouldn't react.
This may have been a misjudgment on the allies' part however, as Kim's comments came before the Foal Eagle military drills -- massive Spring time exercises that are usually accompanied by a major spike in tensions -- not Max Thunder.
Despite some concessions to Pyongyang -- reducing access to journalists, so as to avoid photos of the drills being splashed over South Korean newspapers -- last week North Korea threatened to cancel the summit with Trump over the "provocative military disturbances with South Korea."
A report by the state-run Korean Central News Agency (KCNA) said the drills were against the Panmunjom Declaration signed by Kim and South Korean President Moon Jae-in last month -- wherein the two countries agreed to cease all hostile acts against each other.
Despite angry missives taking aim at US Vice President Mike Pence and Trump's national security adviser John Bolton, North Korea appeared to have swallowed its objections to Max Thunder however. On Thursday it followed through with the promised destruction of the Punggye-ri nuclear site.
This did not stop Trump himself calling off the Singapore summit hours later, saying it would be "inappropriate" at this time.
In response, Pyongyang -- which days ago warned of a potential "nuclear showdown" -- said it was still ready to sit down with the US leader "at any time."
Correction: This story has been updated to give the correct Fighter Wing commanded by Col. David Shoemaker.