Russia's somewhat regular drills in these waters are often in response to NATO exercises in the region, in tit-for-tat muscle flexing. Some EU policy wonks have of late begun to call the Baltic "NATO's lake" in a direct challenge to Moscow.

"The Ocean Shield-2023 naval exercises have begun in the Baltic Sea," Russia's Defense Ministry (MoD) confirmed in a statement, detailing that in total some 6,000 personnel are taking part, operating 30 warships and boats, along with 20 support vessels. 

"During the drill, measures will be worked out to protect sea lanes, transport troops and military cargo, as well as to defend the sea coast, the statement added. "In total, it is planned to perform more than 200 combat exercises, including with the practical use of weapons."

The Baltic Sea coastline is also very important to Russia as its strategic Kaliningrad exclave sits on it, sandwiched between two NATO members, Poland and Lithuania.

The timing of the new drills is additionally important lest Brussels begins to see the Baltic as "NATO's lake"—as Politico recently referred to it, echoing policy thinkers in Europe:

A resurgent NATO is set to tighten its grip on the Baltic Sea, complicating a vital transit route for Vladimir Putin's navy in Russia's backyard...

"[Sweden and Finland] make NATO much more geographically coherent. The Baltic Sea becomes a NATO lake, which is generally useful, also because of the Arctic's increased importance," said Ulrike Franke, a senior fellow at the European Council on Foreign Relations.