Lithuania fears a Russian invasion. Now, it wants to build a border fence.

After the Soviet Union sacrificed millions of lives to help defeat Nazi Germany, it received a token of gratitude from its allies: a chunk of territory surrounding the Prussian city of Konigsberg on the Baltic Sea. Now called Kaliningrad, the isolated and highly militarized Russian enclave of nearly 1 million people is provoking renewed fears of war in Europe.

Following a Russian military buildup in Kaliningrad over the past few months, neighboring Lithuania announced on Monday that it would build an 80-mile-long border fence equipped with surveillance cameras, scheduled to be finished later this year. “The reasons are both economic to prevent smuggling and geopolitical to strengthen the E.U.’s external border,” Interior Minister Eimutis Misiunas told the Agence France-Presse news agency. The project is expected to be funded mostly by the European Union as a security investment.

The fence is the latest sign of the heightened tensions between Russia and the West along the Baltic Sea. All three of the tiny Baltic states — Estonia, Latvia and Lithuania — are members of the E.U. and NATO. They also border Russia and were all once part of the Soviet Union.