Europe’s security landscape has undergone a rapid transformation over the past years. With new threats in cyberspace, aggression from Russia and a war in Syria, it is safe to say that geopolitics is back. This also raises questions about the way we organise Europe’s security, and particularly the cooperation between the EU and NATO. Who should take the lead in safeguarding Europe’s security? What capabilities should be developed to do so? And what should be the balance of competences between the EU, NATO, and the Member States. To facilitate this discussion, the European Liberal Forum launches an e-series, in which liberal voices can comment on the previously mentioned questions. The publication will focus on the relationship between the EU and NATO, and on how, from a liberal point of view, cooperation between the two should look like in the future. Prominent stakeholders have been invited to contribute to the series, which is an on-going work that started at the 2016 ALDE Congress in Warsaw. The first two chapters of this series have been written respectively by ALDE Party President, Hans van Baalen MEP, and by former Ukraine Defence Minister, Anatoliy Grytsenko. Further chapters will be added to the e-series throughout the year. Through continuous discussion, we hope to highlight different liberal perspectives and find common approaches. I hope this e-publication will contribute to a fruitful discussion and wish you all an informative e-reading.