The following 21 forts make up the Metaxas Line, ordered from West to East along the Greco-Bulgarian border.

1. Popotlivitsa (Ποποτλίβιτσα)
2. Istibey (Ιστίμπεη)
3. Kelkagia (Κελκαγιά)
4. Arpalouki (Αρπαλούκι)
5. Paliouriones (Παληουριώνες)
6. Roupel (Ρούπελ)
7. Karatas (Καρατάς)
8. Kali (Κάλη)
9. Persek (Περσέκ)
10. Babazora (Μπαμπαζώρα)
11. Maliaga(Μαλιάγκα)
12. Perithori(Περιθώρι)
13. Partalouska (Παρταλούσκα)
14. Ntasavli (Ντάσαβλη)
15. Lisse (Λίσσε)
16. Pyramidoeides (Πυραμιδοειδές)
17. Kastilo (Καστίλο)
18. Agios Nikolaos (Αγιος Νικόλαος)
19. Bartiseva (Μπαρτίσεβα)
20. Echinos (Εχίνος)
21. Nymfaia (Νυμφαία)

Before the outbreak of World War II, the additions made to the Roupel Fortress were considered to be too weak. Thus, it was decided that further fortifications should be constructed, not only in that particular region, but also along the entire northern Greek borderline. The plans were drawn up in 1935 and work began at Kerkini in 1936. The original intention was that the full fortifications' line reach as far along the border as Ormenion. Greece, however, became involved in World War II in 1940, thus preventing completion. At the war's outbreak, the fortification line had only reached Komotini, Thrace and was 155 km long.

Like the Maginot Line on the Franco-German border, the Metaxas Line was outflanked by German forces specifically when the Germans invaded Greece in April 1941 through Yugoslavia. The German XVIII Mountain Corps and XXX Army Corps attacked the Metaxas Line before dawn on 6 April, but they encountered fierce resistance under the leadership of Brig. General Konstantinos Th. Bakopoulos, and after three days of fighting they had only limited successes. The 2nd Panzerdivision XVIII Mountain Corps with an enveloping move crossed the Yugoslavian borders, overcame Yugoslav and Greek resistance and captured Thessaloniki on the 9th of April. The capture of Thessaloniki forced the Greek East Macedonia Army Section to surrender on the 10th of April and the Metaxas Line battle was over.

German General Wilhelm List, who led the attack against the Metaxas Line, admired the bravery and courage of these soldiers. He refrained from taking the Greek soldiers prisoner and declared that the army was free to leave with their war flags, on condition that they surrender their arms and supplies. He also ordered his soldiers and officers to salute the Greek soldiers (Beevor 2005, p. 20). There were few troops to defend the line as most of the Greek Army was fighting against the Italians on the Albanian front.

• Greco-Italian War
• 4th of August Regime

• Hellenic Army General Staff / Army History Directorate (Γενικό Επιτελείο Στρατού / Διεύθυνση Ιστορίας Στρατού) (1958). The Struggle in Eastern Macedonia and Western Thrace (Αγώνες εις Ανατολικήν Μακεδονίαν και Δυτικήν Θράκην). The Greek Army during World War II (Ο Ελληνικός Στρατός κατά τον Δεύτερο Παγκόσμιο Πόλεμο).

• Kaufmann, J.E. (1999). Fortress Europe: European Fortifications of World War II. Combined Publishing. ISBN 1-58097-000-1.

• Beevor, A. (2005). Crete: The Battle and the Resistance. John Murray. ISBN 0-7195-6831-5.

• Hellenic Army General Staff / Army History Directorate (Γενικό Επιτελείο Στρατού / Διεύθυνση Ιστορίας Στρατού), Period of WW II, F.629/A/1 (1941). Field report of the Army Section of Eastern Macedonia by Lt. General Konstantinos Bakopoulos, from 2/8/1941 to 4/10/1941.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)

• About the German invasion of Greece
• Bunkermuzeum, maps and ww2 fortifications
• World War II Fortifications in Greece