By the beginning of World War II, he had attained the rank of lieutenant general and was given command of the Army Section of Eastern Macedonia (TSAM) — then a crucial post for the defense of the nation.
In the mid-1930s, he distinguished himself as an impartial Military Commander of Athens, as follows: after the “1935 officers’ attempted coup d’état” on March 1 (Greek: Κίνημα του 1935), he served as ex-officio Presiding Judge at the Court Martial of the leaders accused of organizing the revolt.
At the beginning of World War II, General Bakopoulos was Commanding Officer of the Eastern Macedonia Army Section (TSAM, Τμήμα Στρατιάς Ανατολικής Μακεδονίας).
Meanwhile, the German 2nd Panzer Division (XVIII Mountain Corps) advanced through Yugoslav territory into Greece, headed East, south of the Metaxas Line defenses and captured Thessaloniki on April 9.
Only then did Bakopoulos negotiate an honourable surrender of his troops (at 13:00 hrs on April 10) in order to save his men and prevent the bombing of the vital port city of Thessaloniki.
The battle of the Metaxas Line together with other acts of resistance against the Italian attempted invasion and the German occupation are celebrated annually with school parades and Greek media coverage.
A characteristic assessment of the battle of the Metaxas Line and Fort Rupel, as well as the role of General Bakopoulos to save his men (when defeat was certain) and to prevent the bombing of Thessaloniki is given by Konstantinos I. Despotopoulos, ex president of the Athens/Greek Academy.
[1] At 5:30 a.m. July 25, 1943 Bakopoulos was arrested by the Gestapo, along with four other top-ranking Greek generals (including Field Marshal Alexander Papagos-later to be Prime Minister, 1952–1955), for planning and organizing military and civilian resistance to the Nazi occupation.
Bakopoulos and further insight into Nazi diplomatic and military tactics, consult his book "The Imprisonment of the Five Generals" (Greek: "Η Ομηρία των πέντε αντιστρατήγων") published in Athens in 1948.