Much has been written about significant changes expected over the 15 next years and what is the impact on stability and security, but there is a drive for (medium-term) future events that is frequently unnoticed: NATO is a powerful tool whose adaptation to the security environment has a great impact on the security environment itself. This is classic action-reaction dynamics, certainly, but now it is perhaps happening on a much unknown, slippery terrain. Wrong calculations about what the NATO posture should be may lead to unexpected events affecting allied countries" (and partners" as well) stability and security. In this regard, I believe that NATO adaptation to the security environment has room to be improved. For instance, there is too much emphasis on Deterrence, which in my opinion is oversized and therefore somehow inefficient, while Cooperative Security seems to be unexploited. This internal unbalance in the current NATO Deterrence & Defence posture could become a source of problems in the medium term think on Eastern Europe- as well as a way to miss great opportunities e.g. a potential Capacity Building endeavour in the Sahel region.