Oberstleutnant i.G. Sebastian Hagen joined the German Armed Forces in 2003 and became an officer in the hunting force in 2006. From 2010 to 2012 he served as platoon leader and from 2012 to 2015 as company commander in Jägerbataillon 292 in Donaueschingen. During this time he completed assignments abroad in Afghanistan and Mali.

In 2015 he attended the staff officer course at the command academy of the Bundeswehr in Hamburg and was subsequently entrusted with a job at the infantry training center in Hammelburg. In 2016 he was selected to participate in the General Staff / Admiral Staff course nationally at the leadership academy.

From 2018 to 2020 he was Head of Department in the staff of the German Military Representative to NATO and the European Union in Brussels.

Since 2020 he has served on NATO’s International Military Staff in Brussels.

He completed his studies at the Helmut Schmidt University / University of the Federal Armed Forces in Hamburg in 2006 with a diploma in education. In 2016 he obtained a master’s degree in „Military Leadership and International Security“ at the same university.

He has been a member of the CNSS since 2016 and has been a member of the board since 2019, currently as its deputy chairman.