For a long time a peaceful trade area, the Baltic Sea became a major geopolitical hotspot in recent times. The inland sea forms the natural border between 8 states of the EU and Russia. Many strategic questions and issues arise from this constellation that have to do with gas pipelines, territorial claims and foreign policy influences. It is now clear that the time when the European Union could consider the Baltic Sea as "their lake" is over: Russia intends to reclaim its shores lost with the end of the USSR and is confronting Brussels with an unprecedented challenge. The stakes are indeed high and are not limited to a dispute over sovereignty between rival powers. For Europe, the Baltic Sea is a strategic hydrocarbon supply corridor, and the heated debates over the construction of the NordStream gas pipelines are causing deep discord within the EU member states.