"Moscow fears that Kaliningrad is vulnerable to NATO, which surrounds it. So it has installed weapons systems that, even if they are intended as deterrents, also threaten the Baltics and increase Russia’s ability to cut them off from the rest of Europe.

That has led NATO to expand its own presence in Eastern Europe, which makes Kaliningrad more vulnerable, deepening the cycle.

Scholars call this pattern of escalation a security dilemma. It is considered a major cause of World War I, and is one of the most-studied ways in which countries can stumble into an unwanted conflict."

http://www.nytimes.com/2016/07/22/world/europe/donald-trump-nato-baltics-interpreter.html?_r=1