Well, putting aside my personal bias on this topic (which is not easy considering I was living in Kharkiv when the bombs started dropping), I'd say the best blend of geopolitical Macchiavellianism and some admittedly scant commitment to our ideals would be to do basically what we did in the case of Eagle Squadron and the Flying Tigers in WW2: don't get involved by name, but quietly funnel equipment and some ne'er-do-wells who know how to use it, with the goal of bleeding Russia for as long as possible until they're too worn down to march any further West.