What will the West do if Putin turns his eye to the Baltic States?

With Russia effectively annexing the Crimean Peninsula, one wonders what is next. The western side of the Ukraine with its majority ethnic Russians seems like the next card to fall, which would be a devastating blow to the country, since it would cut off the Ukraine’s land border with the rest of Europe, and effectively leave it isolated against the threats of Dictator Putin. 

But perhaps more intriguing is what are Russia’s intentions concerning Estonia, Latvia and Lithuania—all states which joined the NATO alliance. Obviously these countries are of little threat to Russia by themselves. The problem is that these little countries control most of the right bank of Baltic Sea coast, with Russia controlling only an isolated sliver of land around the port of Kaliningrad. 

It is clear that Russia’s principle reason for wanting control of the Crimea is for strategic naval purposes. No doubt Putin yearns to retake control of the Baltic coast for the same reason. The problem is that NATO is treaty bound to come to the defense of the Baltic States in case of attack. Is the West willing to take on the Russians militarily? Is Putin banking on the West being too “weak” and divided to chance it? One thing that is certain is that  the West needs to strike back with sanctions hard and now before that scenario materializes, if it doesn't wish to go to war--otherwise it will lose all credibility.