After leading the Hellenic Navy General Staff in 2013–2015, he served as the Chief of the Hellenic National Defence General Staff until 14 January 2019, and then, until 9 July 2019, as the Minister of National Defence of Greece.

[2] He has served in a succession of command and staff positions aboard ships, and senior staff positions in the Hellenic Navy and NATO, as well as completing the Underwater Demolition School of the Hellenic Navy's elite Underwater Demolition Command (DYK), which he later commanded, the Advanced Mine Warfare School in Belgium and the US Amphibious Warfare School.

[2] On 7 March 2013, the Government Council for Foreign Affairs and Defence (KYSEA) appointed him to the post of Chief of the Hellenic Navy General Staff.

[5] In December 2018, Apostolakis was quoted at meeting with defence ministry correspondents as saying, "If the Turks land on a Greek rock islet we will flatten it."

He also stated that efforts were focused on avoiding a military conflict with Turkey.