In his influential book Democratic Ideals and Reality Halford John Mackinder summarises his Heartland Theory with the following statement: “Who rules East Europe commands the Heartland; who rules the Heartland commands the World-Island; who rules the World-Island commands the world.” This theory suggests that controlling Eastern Europe is the first crucial step toward global dominance. Although the validity of this theory is debated, the ongoing war in Ukraine serves as a reminder that the region is still relevant and that great power competition over it continues.