Writing in The Fiscal Times, Andrew L. Peek argues that Russia and the former Warsaw Bloc countries around its western periphery are on a collision course leading to something like war. Since many are NATO members, treaty obligations mandate other NATO nations come to their aid.
When Putin finally takes the step into a NATO country, most of the other members will temporize and fail to come to their aid. At that point the "alliance" disintegrates.
There isn't much to keep Russia from invading these nations. They have let their defenses deteriorate under the illusory protection of the NATO umbrella.
This situation will pose a huge dilemma for the U.S. If Putin is as canny as he appears, he'll act before President Obama leaves office. The next president is likely to be less "flexible."