Russian military activity in an exclave wedged between two NATO member states has the Lithuanian military on high alert, according to The Lithuania Tribune.

Kaliningrad is located between Poland and Lithuania along the Baltic Sea coast, and was annexed by Russia from Germany at the end of World War II.

Though separated from mainland Russia by Poland and Belarus, the historical and geographical oddity gives Russia an outlet to the lower Baltic and a potential southern flank in any conflict with the Baltic States — former Soviet properties that are now members of both NATO and the European Union.

On Dec. 8, Lithuania put its military's rapid-response force on a "higher state of preparedness" in light of "a rise in the activity of the Russian Federation's forces in the Kaliningrad region as well as in the western part of the Russian Federation," as one top general told LNK TV.

Lithuania's rapid-response force was established this past October, in the wake of Russia's invasion of eastern Ukraine a couple of months earlier. Lithuania's population is 5.8% Russian, and Russian President Vladimir Putin's meddling in Ukraine is partly predicated on his claim that Russia has the right to intervene to protect Russians in any country.

The Baltic states have been subject to their own share of Russian meddling over the past year: In September, an Estonian intelligence agent was kidnapped from the Russian border. Russian war-ships have also "approached Latvian waters" 50 times in 2014, according to Newsweek.

Kaliningrad is another source of alarm, particularly for Lithuania. In May, Russia suspended a 2001 agreement allowing for Lithuania to perform inspections of Russian military assets in the exclave. Russia deployed short-range ballistic missiles to Kaliningrad starting in 2012, and the oblast is also the home base for the Baltic Sea Fleet — it's the only Russian port along the Baltic that doesn't freeze over during the winter.

Lithuania is concerned about Russian actions in Kaliningrad, immediately to the country's south. Reuters/Ints Kalnins Whatever Russia's doing in Kaliningrad to provoke the state of alert next door may be less about any future military action than about keeping the other countries in the region guessing about Moscow's actions and motives. Russia's has proven increasingly willing to violate the sovereignty of its neighbors in the hopes that its frequent incursions will shift the region's security baseline, making countries accept the realities of a more assertive Moscow.

But this policy depends on Russia's neighbors being unwilling to challenge it, and on various regional players correctly interpreting each other's actions. It could be a matter of time before something as small as the current Kaliningrad buildup leads to a situation that none of them can control.