[2] He took part in the naval operations of the Asia Minor Campaign as a crew member of the battleship Limnos, the destroyer Thyella, and the cruiser Averof, being promoted to Sub-Lieutenant on 20 May 1921.

[2] He held these positions during the Greco-Italian War, participating as captain of the Vasilefs Georgios in the first and third naval raids against Italian shipping in the Straits of Otranto (November 1940 and January 1941 respectively).

[2] Lappas also remained in Greece, and was employed in the Navy General Directorate of the collaborationist government's Ministry of National Defence.

[2] Initially he was appointed captain of the repair ship Ifaistos, before being sent to Britain to oversee the delivery to the Greek navy of four Flower-class corvettes.

[2] From 6 September 1952 he was Chief of the Navy General Staff and head of NATO's COMEDEAST, being promoted to vice admiral on 6 October 1952.

[2] On 13 October 1958, he was recalled to active service as head of King Paul's Military Household, holding the position until 1 November 1960.