My hypothesis is backed up by a wealth of research and practical case studies.It is no coincidence that European policy has also recognized the importance of civilian military cooperation. However, as a conclusion to my study, to launch an academic debate and to support the detailed implementation of policy objectives, I would like to identify five key challenges that need to be addressed to enable private actors to cooperate effectively with the military. These are the following: ‒Challenge 1: The cyber defense of critical infrastructures is typically provided by civilian service providers that are not closely linked to military or civilian governmental cyber defense organizations, and therefore in specific situations, such as war, practical cyber defense of these critical infrastructures is not sufficiently effective. ‒Challenge 2: The majority of the best cybersecurity experts and the civilian companies that employ them have no connection to the military, which means that in a war situation, the protection of national cyberspace and potentially the effectiveness of active operations is not the most effective. ‒Challenge 3: Today’s information technology revolution, e.g. the emergence of artificial intelligence, opens up new perspectives in cyber security, but the application of these technologies in national cyber defense, whether military or civilian, will only become feasible after a longer period in medium-sized countries, which are therefore more exposed to cyber-attacks than other, larger and richer powers.‒Challenge 4: Information sharing on incidents is not only not working smoothly at the European level, but also at the national level, which is an obstacle to more effective national and European cyber defense. ‒Challenge 5: Only a fraction of the potential of bilateral and regional cybersecurity cooperation is exploited, and national cyber capability development typically does not take into account the experience of other countries.