A more specific question is: If any western nation put boots on the ground in the Ukraine; would Russia continue to arm rebels knowing they would likely conflict with non-Ukraine forces?
The Ukraine rebels have released a statement claiming they want to muster over 100,000 troops. The Ukrainian government has had a difficult time against the rebels and has tried using diplomatic approaches multiple times.
Germany and many other western nations do not want to militarily intervene but there have been recent announcements that the US is considering arming Ukraine with some weaponry. If the US could convince its NATO partners to intervene in Ukraine with overwhelming force what would the Russian "volunteers" do in this situation?
Would Russia be forced to pull out or would there be a preference to remain as to not also lose Crimea?