They are based in Alaska, which is both a US state and strategically a rather key location for, among other things, air, including ballistic missile, defense; the defense of Alaska seems to be an ideal role for troops (1) with arctic training, and (2) the capability to rapidly redeploy to address incursions over a very wide area of operations.
In any other presidency, it would be Russia. We had a cold war with them for 40+ years with anticipations that a hot war could start at literally any moment (see the fictional film Red Dawn). But, I don't think that Trump would invade Russia. His priorities are vastly different from any other president, Democrat or Republican.
