Just remembered reading in Samatha Powers' book A PROBLEM FROM HELL that George McGovern (ironically, given his leadership of the anti-war movement during the Vietnam War & running on an anti-war platform during the 1972 election) proposed in 1978 a multilateral humanitarian intervention to remove the Khmer Rouge regime from Cambodia due to their horrendous genocidal atrocities against the Cambodian ppl, to be supported politically & militarily by the Carter admin. McGovern actually proposed a multinational intervention force comprising forces from Malaysia, Thailand, the Philippines, Japan & even Vietnam. Of course, the Carter admin criticised McGovern's proposal on the grounds that such multilateral military intervention was not "a live option", so that any attacks made by the US against the KR regime were exclusively in quite muted diplomatic language.
WI somehow McGovern's planned military intervention had in fact been implemented, with support from the US govt, sometime in 1978, before the Vietnamese launched their own unilateral invasion in Dec 1978/Jan 1979 after KR incusions ?