Many thanks to Arturo Filippo Lorioli for contributing this article.
Royal Yugoslavian Army:
Royal Guard Division 1st Guard Regiment 2nd Guard Regiment Guard Cavalry Brigade Guard Artyllery Regiment 1st Infantry Division "Cerska" 6th Infantry Regiment 27th Infantry Regiment 66th Infantry Regiment 1st Artillery Regiment 3rd Infantry Division "Dunavska" 8th Infantry Regiment 18th Infantry Regiment 57th Infantry Regiment 3rd Artillery Regiment 5th Infantry Division "Sumadiska" 19th Infantry Regiment 59th Infantry Regiment 72nd Infantry Regiment 5th Artillery Regiment 7th Infantry Division "Potinska" 25th Infantry Regiment 34th Infantry Regiment 51st Infantry Regiment 7th Artillery Regiment 8th Infantry Division "Krajinska" 9th Infantry Regiment 74th Infantry Regiment 76th Infantry Regiment 8th Artillery Regiment 9th Infantry Division "Timocka" 14th Infantry Regiment 20th Infantry Regiment 75th Infantry Regiment 9th Artillery Regiment 10th Infantry Division "Bosanska" 10th Infantry Regiment 15th Infantry Regiment 60th Infantry Regiment 10th Artillery Regiment 12th Infantry Division "Jadranska" 11th Infantry Regiment 54th Infantry Regiment 83rd Infantry Regiment 12th Artillery Regiment 13th Infantry Division "Hercegovacka" 29th Infantry Regiment 32nd Infantry Regiment 85th Infantry Regiment 13th Artillery Regiment 15th Infantry Division "Zetska" 38th Infantry Regiment 61st Infantry Regiment 87th Infantry Regiment 15th Artillery Regiment 17th Infantry Division "Vrbaska" 33rd Infantry Regiment 89th Infantry Regiment 90th Infantry Regiment 17th Artillery Regiment 20th Infantry Division "Bregalnicka" 23rd Infantry Regiment 28th Infantry Regiment 49th Infantry Regiment 20th Artillery Regiment 22nd Infantry Division "Ibarska" 4th Infantry Regiment 24th Infantry Regiment 58th Infantry Regiment 22nd Artillery Regiment 25th Infantry Division "Vardarska" 21st Infantry Regiment 46th Infantry Regiment 50th Infantry Regiment 25th Artillery Regiment 27th Infantry Division "Savska" 35th Infantry Regiment 53rd Infantry Regiment 104th Infantry Regiment 27th Artillery Regiment 30th Infantry Division "Osijecka" 17th Infantry Regiment 41st Infantry Regiment 64th Infantry Regiment 30th Artillery Regiment 31st Infantry Division "Kosovska" 30th Infantry Regiment 31st Infantry Regiment 56th Infantry Regiment 31st Artillery Regiment 32nd Infantry Division "Triglavska" 39th Infantry Regiment 40th Infantry Regiment 110th Infantry Regiment 32nd Artillery Regiment 33rd Infantry Division "Licka" 44th Infantry Regiment 91st Infantry Regiment 106th Infantry Regiment 33rd Artillery Regiment 34th Infantry Division "Toplicka" 3rd Infantry Regiment 12th Infantry Regiment 16th Infantry Regiment 34th Artillery Regiment 38th Infantry Division "Deavska" 45th Infantry Regiment 112th Infantry Regiment 128th Infantry Regiment 38th Artillery Regiment 40th Infantry Division "Slavonska" 42nd Infantry Regiment 43rd Infantry Regiment 108th Infantry Regiment 40th Artillery Regiment 42nd Infantry Division "Murska" 36th Infantry Regiment 105th Infantry Regiment 126th Infantry Regiment 42nd Artillery Regiment 44th Infantry Division "Unska" 26th Infantry Regiment 55th Infantry Regiment 121st Infantry Regiment 44th Artillery Regiment 46th Infantry Division "Moravska" 1st Infantry Regiment 62nd Infantry Regiment 92nd Infantry Regiment 46th Artillery Regiment 47th Infantry Division "Dinarska" 13th Infantry Regiment 84th Infantry Regiment 119th Infantry Regiment 47th Artillery Regiment 49th Infantry Division "Sremska" 2nd Infantry Regiment 7th Infantry Regiment 70th Infantry Regiment 49th Artillery Regiment 50th Infantry Division "Drinska" 5th Infantry Regiment 63rd Infantry Regiment 65th Infantry Regiment 50th Artillery Regiment 1st Cavalry Division 2nd Cavalry Brigade 6th Cavalry Brigade 8th Cavalry Brigade 2nd Cavalry Division 1st Cavalry Brigade 5th Cavalry Brigade 7th Cavalry Brigade 3rd Cavalry Division 3rd Cavalry Brigade 4th Cavalry Brigade Sebernika Garrison 145th Infantry Regiment Cattaro Garrison 150th Infantry Regiment 151st Infantry Regiment GHQ Reserve 22nd Infantry Regiment 37th Infantry Regiment 47th Infantry Regiment 48th Infantry Regiment 2nd Granicari Odred (Border Guards "Odred") 1st Granicari Regiment 2nd Granicari Regiment 3rd Granicari Regiment 3rd Granicari Odred (Border Guards "Odred") 4th Granicari Regiment 5th Granicari Regiment 4th Granicari Odred (Border Guards "Odred") 6th Granicari Regiment 7th Granicari Regiment 8th Granicari Regiment 25th Granicari Odred (Border Guards "Odred") 13th Granicari Regiment 14th Granicari Regiment 15th Granicari Regiment 16th Granicari Regiment Other "Odred" (roughly a Brigade, formed by a variable number of Regiments. Unfortunatelly I do not have any detailed organization for them): "Risnjacki" "Licki" "Capljinski" "Trebinjski" "Komski" "Strumicki" "Vlasinski" "Kalnski" "Branicevski" "Pozarevski" "Smederevski" "Savski" "Banatski" "Sencanski" "Suboticki" "Somborski" "Ormoski" "Planinski" "Triglavski" Reserve units: Another 25 Infantry Regiments (I do not know their identification numbers)Royal Yugolsavijan Air Force:
1st Fighter Brigade 2nd Fighter Regiment 31st Squadron (11 x Messerschmitt Bf109E) 51st Squadron (18 x Hawker Hurricane I) 6th Fighter Regiment 32nd Squadron (6 x Rogozarski IK-3) 52nd Squadron (10 x Messerschmitt Bf109E) 2nd Mixed Brigade 4th Fighter Regiment 33rd Squadron (14 x Hawker Hurricane I) 34th Squadron (6 x Hawker Hurricane I and 8 x Ikarus IK-2) 8th Bomber Regiment 68th Squadron (11 x Bristol Blenheim I) 69th Squadron (12 x Bristol Blenheim I) 2nd Mixed Brigade 4th Fighter Regiment 33rd Squadron (14 x Hawker Hurricane I) 34th Squadron (6 x Hawker Hurricane I and 8 x Ikarus IK-2) 8th Bomber Regiment 68th Squadron (11 x Bristol Blenheim I) 69th Squadron (12 x Bristol Blenheim I) 3rd Mixed Brigade 5th Fighter Regiment 35th Squadron (16 x Hawker Fury) 36th Squadron (14 x Hawker Fury) 3rd Bomber Regiment 63rd Squadron (36 x Dornier Do.17K) 64th Squadron (34 x Dornier Do.17K) 4th Bomber Brigade 1st Bomber Regiment 61st Squadron (11 x Bristol Blenheim I) 62nd Squadron (12 x Bristol Blenheim I) 7th Bomber Regiment 66th Squadron (15 x Savoia Marchetti SM.79) 67th Squadron (15 x Savoia Marchetti SM.79) 81st Independent Bomber Squadron (13 x Bristol Blenheim I and some Hawker Hind) 1st, 2nd, 3rd, 4th, 5th, 6th and 7th Reconissance Squadrons (attached to Armies HQs, with a total of about 160 x Potez XXV and other airplanes)Royal Yugolsavijan Navy:
Old (very old! 1899!) Light Cruiser: Dalmacija Destroyers: Dubrovnick Beograd Ljubljana Zagreb Submarines: Hrabri Nebojsca Smeli Osvetnik Old Torpedo Boats: T-1 T-3 T-5 T-6 T-7 T-8 Modern Torpedo Boats: Orjen Velebit Dinara Triglav Suvobor Rudnik Uskok Cetnik Gunboats: Beli Orao Klis Lastavica Neretwa Minesweepers-Minelayers: Malinska Marjan Melije Mljet Mosor Galeb Jestreb Orao Sokol Kobac Labud River Patrol Boats: Vardar Sava Drava Morava Dragor Cer Sisak Sabac Granicar Strazar Submarine Depot Ships: Hvar Sitnica Submaine Rescue Ship: Spasilac Tankers: Perum (oil) Lovcen (water) Royal Yacht: Vila Training Sail Ships: Vila Velebita Jadran Tugs: Snazi Ustrajni Marlijvi Silni Jaki R-1 R-9 R-10 R-13 R-14 R-15 R-16 R-91 R-101 R-102 R-103 R-104 Several small support ships, including: Kozjiak Jadran (same name of the Training ship!) Trogir Naval Air Force: About 150 hydroplanes (including Rogozarski SIM-XIV H, Dornier Do.22, Dornier Wal etc)