The US doesnt have the stomach for an all out conflict with a power(s) that can actually hurt them , Russia most likely doesnt either , they are still the mighty bear , but they are a shadow of a military of what they were during the Soviet Union . Look at the chain reaction that started the first world war . In this case , somebody mentioned the smaller nations , like Romania and Poland . If they went into Poland , Germany would mobilize immediately , they would have to , as their borders would be in direct threat . If Germany mobilized , That would most likely bring the UK , France , and the other larger NATO countries into a similar state . Be interesting to see how this plays out , it may turn out to be not much of anything in the larger picture .