It has been confirmed through US government documents that the US has effectively opposed the situation, saying that a more disastrous situation could occur to the forces plotting a “reverse coup” within the South Korean military to overthrow Chun Doo-hwan, who took power in the 12/12 coup.
Newly declassified data included the US Embassy's report to the US State Department on February 1, 1980, of such anti-coup movements.
The informant was presumed to be Lee Beom-joon, then Assistant Defense Minister at the time, but since he has already passed away, there is no way to directly confirm it, the 5.18 Democratization Movement Fact-finding Investigation Committee said.