Just before 6 a.m. South Korea time Tuesday, North Korea fired an unidentified missile from near the capital Pyongyang, towards the northeast.
It flew over the northern Japanese island of Hokkaido, making it the first North Korean projectile to successfully pass over Japanese territory since 1998. It subsequently broke up and fell into the Pacific Ocean.
Just hours after the launch, South Korea's Presidential Office announced four F-15K jetfighters had dropped eight MK 84 bombs on a simulated target at the Taebaek Pilsung Firing Range in the country's northeastern Gangwon province, about five hours drive from Seoul .
The MK 84 is a 2,000 pound bomb designed to penetrate hardened targets, according to the US Air Force.
Robert Kelly, associate professor at Pusan National University's Department of Political Science, told CNN South Korea's response was a carefully considered escalation.
"North Koreans can't just shoot missiles over people's countries, there has to be some response," Kelly said.
"(It) looks somewhat escalatory, it's got to be tough, to send a signal, but they don't want to be too tough because no one wants to get into a war."
In a press conference, presidential spokesman Yoon Young-chan said South Korean leader Moon Jae-in had wanted "to showcase a strong punishment capability against the North."
An official with the South Korean Defense Ministry told CNN the bombs had all landed on target.
"The drill reconfirmed South Korea Air Force capability to destroy the enemy's leadership in cases of emergency," the official said.
'Most serious and grave ever'
International reaction to North Korea's missile launch was swift. Japanese Prime Minister Shinzo Abe said it was the "most serious and grave" threat to his country.
South Korea joined with the United States and Japan Wednesday in calling for an emergency meeting of the United Nations Security Council to discuss the North Korea launch, Japan's UN ambassador Koro Bessho told CNN.
It will be held on Tuesday afternoon, two UN diplomats told CNN.
"Our goal is to stop North Korea from going down this road. The international community has to put more pressure on North Korea," Ambassador Bessho said.
US President Donald Trump spoke to Abe following the launch, where he reiterated the US stood behind Japan "100 per cent," Abe told reporters.
Launch over Japan shows 'contempt'
Despite the controversial path of North Korea's latest missile launch, experts said the launch probably had very little to do with Japan.
"It definitely expresses contempt for Japan but it's not a threat to them," Josh Pollack, senior research associate at the Middlebury Institute of International Studies at Monterey, told CNN.
"(North Korea) are really confined by their geography. If they're going to launch to a distance they've got to go over somebody. At a bare minimum they've got to go over some small, populated island if you want to test... an ICBM."
With North Korea unwilling to offend its northern neighbor Russia, the logical place for them to fire missiles over is the US-aligned Japan.
"There's nothing to lose," John Delury, associate professor at Yonsei University Graduate School of International Studies, told CNN.
Japan maintains a pacifist constitution that limits the country's forces to defensive purposes only.
"They don't have a good relationship with Japan, there's nothing developing in their relationship with Japan which should cause them to show restraint."