> (Obama's version was surrendering Crimea to Putin so that Putin would give him an out for his Syrian "red line" blunder). What approach would you have taken

> (Obama's version was surrendering Crimea to Putin so that Putin would give him an out for his Syrian "red line" blunder). What approach would you have taken to prevent Vladimir Putin from taking back Crimea? It’s a majority Russian area where they hold a long term naval base lease. The peninsula in question was gifted to Ukraine by the USSR in 1954. Also keep in mind the fact that Russia has nuclear weapons, and any direct military conflict with Russia has the potential to go nuclear. How do you proceed to prevent Russia from annexing Crimea?