Dimitrios Giatzis was born in Lamia in 1891, and enlisted in the Hellenic Army as a volunteer on 12 March 1910.

[2] He subsequently fought on the Macedonian front during World War I and in the Asia Minor Campaign, first as a company commander and later as a staff officer, being promoted to Lieutenant in 1917 and to Captain in 1920.

[2] In the interwar period he served successively as battalion commander, chief of staff of the 3rd Infantry Division, in the staff of II Army Corps, in the Administrative Directorate of the Ministry for Military Affairs, commander of VI Border Sector (1938–40) and briefly chief of staff of the Infantry Inspectorate, before assuming command of III Infantry Brigade in September 1940.

[2] He led III Brigade during the first months of the Greco-Italian War, and was appointed chief of infantry to 8th Infantry Division in January 1941, a post in which he remained until the Greek capitulation following the German invasion of Greece in April.

[2] Following liberation he joined the re-forming Army, and was named briefly commander of the 2nd National Guard Division in January 1945, before assuming command of the 9th Infantry Division in the next month.