edit: at the same time, in the same conflict.
I remember reading a few years ago about a conflict in (I want to say) 1980’s Latin America where this occurred; however I can’t find anything about this with current online search tools. Did I hallucinate this or did this actually, and if so what groups?
there were times where the US funded groups that were leftists as means of countering, to their perception at the time, even more radical communists.
it was more in the way of ‘enemy of my enemy, might still be an enemy, but they’re not the current problem’ than anything else. I don’t think it ever ended the way we wanted it to, or the way that it should have.
As an example, we funded FSLN against the Samoza family, in Nicaragua. we also supported the Derg- an ML military junta- in ethiopia against the Eritrean independence peeps (who were at the time even more communist.
Maybe the United States involvement in regime change in Latin America is what you had in mind?
Or perhaps you’d like to peruse through old CIA files.
It’s not like they backed factions based on ideology…
In virtually everyone of those proxy governments it was a dictator who agreed to back one side or the other
The closest I can think of: I think there was a crazy time when the People’s Republic of China and, to a lesser extent, the US were together(!) backing “Democratic Kampuchea” (i.e. the Khmer frickin’ Rouge) against the invading (USSR-allied) Socialist Republic of Vietnam and its proxy, the People’s Republic of Kampuchea.
So, the US, softly, backing a bunch of far-left lunatics against a less-far-left bunch backed indirectly by the Soviets.
From Wikipedia
The Cambodian–Vietnamese War was an armed conflict between the Khmer Rouge-led Democratic Kampuchea and the Socialist Republic of Vietnam. It began in December 1978, with a Vietnamese invasion of Cambodia which toppled the Khmer Rouge and ended in 1989 with the withdrawal of Vietnamese forces from Cambodia. This Cold War conflict was part of the Third Indochina War and Sino-Soviet split with the Soviet Union supporting Vietnam and China supporting the Khmer Rouge.
The Nigerian civil war was insane