This book tests two competing hypotheses concerning the growing role of interdemocratic security institutions in Europe since the collapse of the Soviet Union, and the ensuing contributions they made to the security dilemma with Russia. A key objective is to introduce a theoretical framework for analysing contributions to a security dilemma by one side in a dyad. Most contemporary academic debates devoted to security relations between the EU/NATO and Russia tend to be descriptive rather than theory driven. Despite the similarities of the exclusive and ideological characteristics of both the EU and NATO, most scholars do not tend to conceptualise the EU and NATO collectively as inter-democratic security institutions. Also, despite the rise of the EU and NATO as the main actors shaping the European security architecture, the point of departure for most analyses tend to be the Russian challenge to the EU and NATO. The effect of the rise of inter-democratic security institutions on the security dilemma with Russia as a non-member state is an essential research area within European security, unless it is assumed that Russian foreign policy is shaped independently from this phenomenon. Russia constitutes a unique case as it is the largest European state and most likely to be the only state permanently excluded from full membership in both the EU and NATO. The book assesses how and why inter-democratic security institutions influence the variables that aggravate or mitigate the security dilemma.