South Korea's National Security Adviser Chung Eui-yong and intelligence chief Suh-hoon are the men behind the diplomatic breakthrough between North Korea and the US.
The two officials were part of a delegation which visited Pyongyang this week as guests of North Korean leader Kim Jong-un. And now, they have relayed Pyongyang's message to Donald Trump, with apparent success.
What do we know about these men, handpicked by South Korean President Moon Jae-in to be the special envoys?
National Security Adviser (NSA) Chung Eui-yong, 71, is an experienced diplomat who has worked closely with the US.
He was the foreign policy adviser during Moon Jae-in's presidential election campaign and was named South Korea's national security adviser in May 2017.
President Moon described Mr Chung as the "right man" for the NSA's job.
"I believe one of the most important aspects the country's security adviser should have is a firm mind on security and diplomatic abilities when we face diplomatic and economic issues tied together, including North Korea's nuclear programme, THAAD [the US missile defence system in South Korea] and free trade agreements," Mr Moon said at the time.
Mr Chung describes his US counterpart Gen H R McMaster as "my close friend" and has worked alongside him in the aftermath of North Korea's nuclear test in September 2017 and subsequent missile tests.
The Yonhap news agency says that Mr Moon's decision to send Mr Chung to Pyongyang was "part of his efforts to pave the way for dialogue between Pyongyang and Washington, seen as crucial in setting the stage for an inter-Korean summit".
National Intelligence Service chief Suh Hoon, 63, has played a key role in making previous inter-Korean talks happen.
He held secret negotiations with the North to prepare for the landmark summits in June 2000 and October 2007.
He has also met late North Korean leader Kim Jong-il several times between 2002 and 2007.
Mr Suh seems to have impressed Kim Jong-il as the North Korean leader "once praised him for his diligence", the Chosun Ilbo newspaper cited an official from South Korea's Ministry of Unification as saying.
Mr Suh was in North Korea between 1996 and 1999 as the head of the field office of the Korean Peninsula Energy Development Organization (KEDO). This is when he picked up the skills to negotiate with North Korean officials.
KEDO was set up to implement a 1994 deal under which North Korea promised to freeze and ultimately dismantle its nuclear programme in exchange for energy-producing light water reactors and other concessions from the US.
After returning home, Mr Suh was involved in secret contacts with Pyongyang for the summit talks in 2000 between then President Kim Dae-jung and the North's Kim Jong-il.
During the Roh Moo-hyun administration, he also accompanied then spy chief Kim Man-bok on a trip to North Korea to prepare for the 2007 summit between Roh and Kim Jong-il.