Spoiler - they didn't.
Obama has no foreign policy.
Except for a counter-response to a nuclear attack on the South, Obama won't have much influence on ROK's foreign policy vis-a-vis its enemy to the north.
By policy, the 8th Army (US forces) will coordinate with ROK forces. If combat elements of the 101st Airmobile (as opposed to planning cadre) suddenly start heading for the West Coast, you can figure that everybody is getting seriously serious about the situation in Korea.
Chechens are now fighting with the Ukrainian forces against the Russians. Here's an interview with one of their leaders. Very interesting. These guys really hate the Russians.
https://news.vice.com/article/meet-...der-battling-russia-with-some-unlikely-allies
Wait. Islamists and former Nazi supopoirters banding together.to fight the Ruskies????? Can they all lose?