This article reflects the discussions during a September 2018 conference in Sofia, sponsored by the NATO Public Diplomacy Division. Its focus is on the defense and deterrence posture of NATO and the European Union in Eastern Europe. Special attention is given to the development of the Bucharest Initiative (B9) and its influence on the Western Balkans and Black Sea Region. The authors propose a Program for Readiness and Interoperability, oriented to the C4ISR area. This is based on the defense posture and in the context of the developments in NATO and the European Union for improved readiness and interoperability with partners that, together with enhanced cooperation in education and training for the de¬fined B9+ region, will act as instruments to implement this cooperation and improve the deterrence and defense capability on the Eastern Flank of NATO and the EU, while at the same time strengthening resilience to hybrid threats.