Mr.Diakopoulos has served in various positions in Naval Units and Headquarters of the Hellenic Navy as Staff Officer, Head of Department and Director of several Directorates in Hellenic Navy Helicopter Command (HNHC), Fleet Command and Hellenic Navy General Staff. Additionally, he has served as Naval Attaché of Greece in Ankara (TURKEY) and Chief of Staff of the Hellenic Navy Helicopter Command (HNHC). He has also served in the Chief’s of the Navy Bureau as “Public Information Officer”, from 2002 to 2005. His Command posts include the posts of Commanding Officer of MSC AIDON (M-248), from 1995 to 1997 and HS PROMITHEUS (A-374), from 2006 to 2007, as well as Commanding Officer of Hellenic Navy Helicopter Pilot School (HNHPS), from 1998 to 2000, and of the Hellenic Navy Helicopter Command (HNHC), from 2011 to 2013. Upon promotion to the rank of Commodore he was posted as Director of International Affairs Branch in the Hellenic National Defence General Staff, from 2013 to 2014. On December 4th 2014 he was assigned by the Minister of Defence, as Alternate General Director of National Defence Policy and International Relations Directorate at the Hellenic Ministry of National Defence. Following his promotion to Rear Admiral on October 16th 2015, he was assigned Commander of Naval Training and Education.
On September 12th 2016, while taking on his duties as Commander of Naval Training, he was also assigned as Superintendent of Hellenic Naval Academy. Following his promotion to Vice Admiral on January 16th 2017, he was assigned as Commandant of National Defense College simultaneously with the duties of Commander of Naval Training and Superintendent of Hellenic Naval Academy. From March 8th 2017 till February 8th 2019 he has served as Commandant of the National Defense College. On February 8th 2019 he retired holding the title of Emeritus Commandant of the National Defense College.