What is the motive of the Russian invasion of Ukraine? Is Kreml seaking security or power? The topic will be discussed from the perspective of offensive and defensive realism, which is based on John Mearsheimer, Stephen Walt and Kenneth Waltz thoughts and ideas. The thesis has also studied the war in Georgia and Syria in an attempt to find similarities with today's war in Ukraine. The thesis is structured as a comparative case study with a theory testing element with an main focus of explaining the invasion from offensive and defensive realism. The thesis can conclude that the motive behind the invasion could be explained by both theories with a clear predominance of a desire for power.