ALLIES:
British
- Fighters
- Bristol Blenheim Mk.IF
- Gloster Gladiator Mk.I
- Gloster Gladiator Mk.II
- Hawker Hurricane Mk.I
- Bombers
- Bristol Blenheim Mk.I
- Bristol Blenheim Mk.IV
- Fairey Swordfish
- Vickers Wellington
- Reconnaissance
- Westland Lysander
- Short Sunderland
Greek
- Fighters
- Bloch 151
- Gloster Gladiator Mk.I
- Gloster Gladiator Mk.II1
- PZL P.24
- Bombers
- Bristol Blenheim Mk.I
- Bristol Blenheim Mk.IV
- Fairey Battle
- Potez 633 B2
- Reconnaissance
- Avro Anson
- Dornier Do.22G
AXIS:
Yugoslavian
- Fighters
- Avia BH-33E
- Hawker Fury Mk.II
- Hawker Hurricane Mk.I
- Ikarus IK-2
- Messerschmitt Bf 109E-3a
- Rogozarski IK-3
- Bombers
- Bristol Blenheim Mk.I
- Dornier Do 17K
- Hawker Hind
- Savoia-Marchetti SM.79-I
- Reconnaissance
- Bregeut Bre.19
- Dornier Do 15
- Dornier Do 22K
- Potez 25
- Rogozarski Sim XIV
Under pressure from Hitler, Yugoslavia signed the Tripartite Pact to join the Axis on March 25, 1941. There was strong anti-German sentiment among the country's Serbians, however, so the Yugoslavian government was overthrown in a military coup d'etat on the 26th. This enraged Hitler. The new Yugoslavian government doubted the British could help them, so they told Hitler they would not cancel any standing agreements, although they would not ratify their adherence to the Tripartite Pact. Hitler did not trust them, so he directed that planning for his impending surprise invasion of Greece through Bulgaria be widened to include a multi-pronged surprise invasion of Yugoslavia. This caused Operation Barbarossa, Hitler's impending attack against the Soviet Union, to be postponed from May until June.
AXIS:
German
- Fighters
- Messerschmitt Bf 109E
- Messerschmitt Bf 110C
- Messerschmitt Bf 110D
- Bombers
- Dornier Do 17Z
- Heinkel He 111P
- Henschel Hs 123A
- Junkers Ju 87B Stuka
- Junkers Ju 88A-5
- Reconnaissance
- Henschel Hs 126A
- Fieseler Fi 156 Storch
- Junkers Ju 88D
- Troop Insertion
- Junkers Ju 52/3m
Hungarian
- Fighters
- Fiat CR.32
- Fiat CR.42
- Bombers
- Caproni Ca.135bis
- Junkers Ju 86K-2
- Reconnaissance
- Heinkel He 46
- Heinkel He 170
- WM 21
- Troop Insertion
- Savoia-Marchetti SM.75
Italian
- Fighters
- Fiat CR.42
- Fiat G.50bis
- Macchi C.200
- Bombers
- Cant Z.1007bis
- Fiat BR.20
- Junkers Ju 87B Stuka
- Savoia-Marchetti SM.79-II
- Reconnaissance
- Cant Z.506B
- Caproni Ca.311
- Fieseler Fi 156 Storch
- IMAM Ro.37bis
Although many of the German troops in this campaign launched their attacks from Romania and Bulgaria, those two Axis countries did not participate in the invasions of Yugoslavia and Greece. Romania had no interest in Yugoslavian territory, and wanted its military forces available to defend against a possible Soviet attack. Hitler had informed Bulgaria in November, 1940, that he wanted to attack Greece by moving his troops through Bulgaria, but the Bulgarians were wary of becoming militarily involved in the war. Although the Bulgarians allowed the Germans to make preparations to enter their country, they repeatedly postponed signing the Tripartite Pact until the last moment. They were particularly worried about provoking neighboring Turkey, and didn't become an official member of the Axis until March 1, allowing German troops to enter their country the next day. This prompted the Greeks to finally ask the British to send ground troops into Greece. The Germans rewarded the Bulgarians for their cooperation by allowing them to occupy eastern regions of Greece and Yugoslavia after these areas were conquered by German troops.
