Please feel free to comment or fill in any of the gaps, but note that some ranks cannot be expressed against others; I've done my best to align them sensibly. There is inevitably some rank structure which overlaps into one above or one below, where no direct comparison is possible.
United States Marine Corps ranks are as per the United States Army, with minor variations.
The Geheimstatspolizei (Gestapo) and Sicherheitsdienst (SD) ranks are the same as, or very similar to, those of the Waffen-SS.
· Other Ranks; Non-Commissioned Officers; Senior Non-Commissioned Officers; Boy Officers; Commissioned Officers; Senior Commissioned Officers; Air/Sea/Field Grade Officers; Commanders
Royal Air Force = Aircraftman 2nd Class (AC2)
Women's Auxiliary Air Force = Aircraftwoman 2nd Class (ACW2)
Royal Navy = Ordinary Seaman
Women's Royal Naval Service = Wren
British Army = Private; Sapper; Fusilier, Gunner; Rifleman
United States Army and Army Air Force = Private
United States Navy = Seaman Recruit
Kriegsmarine = Matrosengefrieter
Wehrmacht = Schutze; after Nov. 1942, Grenadier
Waffen-SS = SS-Schutze
Luftwaffe = Flieger, Gefrieter
Red Army Air Force = Krasnoarmeyets
Polish Air Force = Szeregowiec
Finnish
Army & Air Force : Sotamies; Kiväärimies, Tykkimies, Pioneeri,
Lentosotamies
Finnish Navy : Matruusi
Royal Air Force = Aircraftman 1st Class (AC1)
Women's Auxiliary Air Force = Aircraftwoman 1st Class (ACW1)
Royal Navy = Able Seaman
United States Army and Army Air Force = Private 1st Class (PFC)
United States Navy = Seaman Apprentice
Kriegsmarine = Matrosenobergefrieter
Wehrmacht = Oberschutze
Waffen-SS = SS-Oberschutze
Luftwaffe = Obergefrieter
Red Army Air Force = Yefreyto
Polish Air Force = Starszy Szeregowiec
Royal Air Force = Leading Aircraftman (LAC)
Women's Auxiliary Air Force = Leading Aircraftwoman (LACW)
British Army = Lance-Corporal; Lance-Bombardier
United States Navy = Seaman
Kriegsmarine = Matrosenhauptgefrieter, Matrosenstabsgefrieter, Matrosenoberstabsgefreiter
Wehrmacht = Gefreiter
Luftwaffe = Hauptgefrieter
Polish Air Force = Kapral
Finnish Army & Air Force : Korpraali
Finnish Navy : Ylimatruusi
Royal Air Force / Women's Auxiliary Air Force = Corporal
Royal Navy = Leading Seaman
Women's Royal Naval Service = Leading WREN
British Army = Corporal; Bombardier
United States Army and Army Air Force = Corporal
United States Navy = Petty Officer 3rd Class
Kriegsmarine = Steurmann, Obermaat, Maat
Wehrmacht = Obergefreiter
Waffen-SS = SS-Sturmmann
Luftwaffe = Unteroffizier
Red Army Air Force = Mladshiy Serzhant (Junior Sergeant)
Polish Air Force = Plutonowy
Finnish Army, Navy & Air Force : Alikersantti
Senior Corporal = Stabsgefreiter
Lance-Sergeant = Unteroffizier, Unterfeldwebel
Royal Air Force / Women's Auxiliary Air Force = Sergeant
Royal Navy / Women's Royal Naval Service = Petty Officer
British Army = Sergeant
In the British Army during the First World War, this rank was written Serjeant, and appears thus on Commonwealth War Graves headstones and official documentation.
United States Army and Army Air Force = Sergeant
United States Navy = Petty Officer 2nd Class
Kriegsmarine = Stabssteurmann
Wehrmacht = Unterfeldwebel
Waffen-SS = SS-Hauptscharfuhrer
Luftwaffe = Feldwebel
Red Army Air Force = Serzhant
Polish Air Force = Sierzant
Finnish Army, Navy & Air Force : Kersantti
I appreciate that the rank of Sergeant-Major has a very wide internal hierarchy with both distinct and subtle differences of rank. These alone warrant a page to themselves, so I trust readers will allow me, for the sake of brevity, to place them all in one group.
Royal Air Force / Women's Auxiliary Air Force = Flight Sergeant
British Army = Sergeant-Major, Warrant Officer Class 2
United States Army and Army Air Force = Staff Sergeant; Technical Sergeant is a higher grade
United States Navy = Petty Officer 1st Class
Free French Air Force = Sergent Chef
Kriegsmarine = Obersteurmann
Wehrmacht = Oberfeldwebel, Stabsfeldwebel, Stabswachtsmeister
Waffen-SS = SS-Sturmscharfuhrer
Luftwaffe = Oberfeldwebel
Red Army Air Force = Starshiy Serzhant (Senior Sergeant); Starshina also roughly corresponds to this rank.
Polish Air Force = Starszy Sierzant
Finnish Army, Navy & Air Force : Ylikersantti
Royal Air Force / Women's Auxiliary Air Force = Warrant Officer
This is an unusual rank in the RAF in that holders of Warrant Officer status were addressed as "Sir" or "Ma'am" by Other Ranks, and addressed as "Mr", "Miss" or "Mrs" by Commissioned Officers. Yet they ate with Non-Commissioned Officers in the Sergeants' Mess and bunked with other NCOs.
The Royal Canadian Air Force had two grades of Warrant Officer, W/O1 and W/O2.
Royal Navy = Chief Petty Officer
Women's Royal Naval Service = Chief Wren
British Army = Warrant Officer Class 1
United States Army and Army Air Force = Top Sergeant; Sergeant 1st; 1Sgt
United States Navy = Chief Petty Officer
Free French Air Force = Adjudant
Kriegsmarine = Stabsobersteurmann
Luftwaffe = Oberfeldwebel
Red Army Air Force = Mladshiy Leytenant (Junior Lieutenant) This rank also roughly corresponds with Midshipman.
Polish Air Force = Chorazy
Finnish Army & Air Force : Vääpeli
Finnish Navy : Pursimies
Senior Warrant Officer, Finnish Army & Air Force : Ylivääpeli
Senior Warrant Officer, Finnish Navy : Ylipursimies
Chief Warrant Officer, Finnish Army, Navy & Air Force : Sotilasmestari
Royal Air Force, British Army & Women's Royal Naval Service = Cadet
Royal Navy = Midshipman
US Navy Officer Cadets = Midshipman
Luftwaffe, Kriegsmarine, Wehrmacht = Fahnrich, Senior Cadet = Oberfahnrich
Waffen-SS = SS-Junker, Senior Cadet = SS-Oberjunker
Finnish Army, Navy & Air Force : Kadetti
Note that in other than the British, Canadian, Australian and Free French armed forces, the rank of Lieutenant (pronounced "Lef-tenant") is pronounced "Loo-tenant".
Royal Air Force = Pilot Officer
Women's Auxiliary Air Force = Assistant Section Officer
Royal Navy = Sub-Lieutenant
Women's Royal Naval Service =3rd Officer
British Army = 2nd Lieutenant
United States Army and Army Air Force = 2nd Lieutenant
United States Navy = Ensign
Free French Air Force = Sous-Lieutenant
Kriegsmarine = Leutnant zur See
Wehrmacht = Leutnant
Waffen-SS = SS-Untersturmfuhrer
Luftwaffe = Leutnant
Red Army Air Force = Leytenant
Polish Air Force = Podporucznik
Finnish Army & Air Force : Vänrikki
Finnish Navy : Aliluutnantti
Royal Air Force = Flying Officer
Women's Auxiliary Air Force = Section Officer
Women's Royal Naval Service = 3rd Officer
British Army = Lieutenant
United States Army and Army Air Force = 1st Lieutenant
United States Navy = Lieutenant JG (Junior Grade)
Free French Air Force = Lieutenant
Wehrmacht = Oberleutnant
Kriegsmarine = Oberleutnant zur See
Waffen-SS = SS-Obersturmfuhrer
Luftwaffe = Oberleutnant
Red Army Air Force = Starshiyi Leytenant (Senior Lieutenant)
Polish Air Force = Porucznik
Finnish Army, Navy & Air Force : Luutnantti
Senior Lieutenant, Finnish Army, Navy & Air Force : Yliluutnantti
Note that the title 'Captain' when referring to the master of a ship or aircraft is not an actual rank.
Royal Air Force = Flight Lieutenant
Women's Auxiliary Air Force = Flight Officer
Royal Navy = Lieutenant
Women's Royal Naval Service = 2nd Officer
British Army = Captain
United States Army and Army Air Force = Captain
United States Navy = Lieutenant
Free French Air Force = Capitaine
Kriegsmarine = Kapitänleutnant
Wehrmacht = Hauptmann, Rittmeister
Waffen-SS = SS-Hauptsturmfuhrer
Luftwaffe = Hauptmann
Red Army Air Force = Kapitan
Polish Air Force = Kapitan
Finnish Army, & Air Force : Kapteeni
Finnish Navy : Kapteeniluutnantti
Royal Air Force = Squadron Leader
Women's Auxiliary Air Force = Squadron Officer
Royal Navy = Lieutenant-Commander
Women's Royal Naval Service = 1st Officer
British Army = Major
United States Army and Army Air Force = Major
United States Navy = Lieutenant-Commander
Free French Air Force = Commandant
Kriegsmarine = Korvettenkapitän
Wehrmacht = Major
Waffen-SS = SS-Sturmbannfuhrer
Luftwaffe = Major
Red Army Air Force = Major
Polish Air Force = Major
Finnish Army & Air Force : Majuri
Finnish Navy : Komentajakapteeni
Royal Air Force = Wing Commander
Women's Auxiliary Air Force = Wing Officer
Royal Navy = Commander
Women's Royal Naval Service = Chief Officer
British Army = Lieutenant-Colonel
United States Army and Army Air Force = Lieutenant-Colonel
United States Navy = Commander
Wehrmacht = Oberstleutnant
Kriegsmarine = Fregattenkapitän
Waffen-SS = SS-Obersturmbannfuhrer
Luftwaffe = Oberstleutnant
Red Army Air Force = Podpolkovnik
Polish Air Force = Podpulkownik
Finnish Army & Air Force : Everstiluutnantti
Finnish Navy : Komentaja
Royal Air Force = Group Captain
Women's Auxiliary Air Force = Group Officer
Royal Navy = Captain
Women's Royal Naval Service = Superintendant
British Army = Colonel
United States Army and Army Air Force = Colonel
United States Navy = Captain
Kriegsmarine = Kapitan zur See
Wehrmacht = Oberst
Waffen-SS = SS-Standartenfuhrer
Luftwaffe = Oberst
Red Army Air Force = Polkovnik
Polish Air Force = Pulkownik
Finnish Army & Air Force : Eversti
Finnish Navy : Kommodori
The Waffen-SS has the rank of Oberfuhrer which lies between Colonel and Brigadier.
Royal Air Force = Air Commodore
Women's Auxiliary Air Force = Air Commandant
Royal Navy = Commodore 2nd Class also, Commodore 1st Class
Women's Royal Naval Service = Deputy Director
British Army = Brigadier
United States Army and Army Air Force = Brigadier
United States Navy = Rear-Admiral (Lower Half) also sometimes referred to as Commodore
Kriegsmarine = Konteradmiral
Wehrmacht = GeneralMajor
Waffen-SS = SS-Brigadefuhrer
Luftwaffe = Generalmajor
Royal Air Force = Air Vice-Marshal
Women's Auxiliary Air Force = Air Chief Commandant
Royal Navy = Rear-Admiral
Women's Royal Naval Service = Director, WRNS
British Army = Major-General
United States Army and Army Air Force = Major General
United States Navy = Rear-Admiral (Upper Half)
Kriegsmarine = Vizeadmiral
Wehrmacht = General-Leutnant
Waffen-SS = SS-Gruppenfuhrer
Luftwaffe = GeneralLeutnant
Red Army Air Force = General Leytenant
Polish Air Force = General Brygady
Finnish Army & Air Force : Kenraalimajuri
Finnish Navy : Kontra-amiraali
Royal Air Force = Air Marshal
Royal Navy = Vice-Admiral
Women's Royal Naval Service = Chief Commandant
British Army = Major-General
United States Army and Army Air Force = Lieutenant-General
United States Navy = Vice-Admiral
Kriegsmarine = Admiral
Wehrmacht = General
Waffen-SS = SS-Obergruppenfuhrer
Luftwaffe = General
Red Army Air Force = Lieutenant-General
Polish Air Force = General Dywizji
Finnish Army & Air Force : Kenraaliluutnantti
Finnish Navy : Vara-amiraali
Royal Air Force = Air Chief Marshal
Royal Navy = Admiral
British Army = General
United States Army and Army Air Force = General
United States Navy = Admiral
Kriegsmarine =Generaladmiral
Wehrmacht = General-Oberst
Waffen-SS = SS-Oberstgruppenfuhrer
Luftwaffe = Generaloberst
Red Army Air Force = General Polkovnik
Polish Air Force = General Broni
Finnish Army & Air Force : Kenraali
Finnish Navy : Amiraali
Red Army Air Force = Marshal Aviatsiyi (Air Marshal).
Royal Air Force = Marshal of the Royal Air Force
Royal Navy = Admiral of the Fleet
British Army = Field Marshal
United States Army and Army Air Force = General of the Army
Note the USAAF rank is General of the Army for the WW2 period as the Air Force was actually the Army Air Force at that time.
United States Navy = Fleet Admiral
Kriegsmarine = Grossadmiral
Wehrmacht = Generalfeldmarschall
Luftwaffe = Generalfeldmarschall
Red Army Air Force = Glavnyy Marshal Aviatsiyi (Supreme Air Marshal)
Polish
Air Force = General Armiyi
(Army General)”
Finnish Armed Forces : Marsalkka
In the US Armed Forces, the ranks of General of the Air Force, General of the Army and Fleet Admiral are referred to by the US as Five Star ranks. Such were created during WW2 to give parity with the British Commonwealth rank of Field Marshal, Marshal of the RAF, and Admiral of the Fleet, and are very rarely awarded.
Luftwaffe = Reichsmarschal
Waffen-SS = Reichsfuhrer-SS
Red Army Air Force = Marshal Sovyetskogo Soyuza (Marshal of the Soviet Union)
There is a less complicated list than this ...
Military Ranks Explained
General / Air Chief
Marshal / Admiral
... leaps tall buildings in a single bound
... is more powerful than a locomotive
... is faster than a speeding bullet
... walks on water
... gives policy to God.
Colonel / Group Captain / Captain
... leaps short buildings in a single bound
... is more powerful than a switch engine
... is just as fast as a speeding bullet
... walks on water if the sea is calm
... talks with God.
Lieutenant-Colonel / Wing Commander / Commander
... leaps short buildings with a running start and a favouring wind
... is almost as powerful as a switch engine
... slower than a speeding bullet
... walks on water in an indoor swimming pool
... talks with God if special request is approved.
Major / Squadron Leader / Lieutenant-Commander
... barely clears Nissen Hut
... loses tug'o'war with locomotive
... can fire a speeding bullet
... swims well
... is occasionally addressed by God.
Captain / Flight Lieutenant / Lieutenant
... makes high marks when trying to jump buildings
... is run over by locomotive
... can sometimes handle a gun without inflicting self injury
... dog paddles
... talks to some animals.
1st Lieutenant / Flying Officer / Lieutenant
... runs into buildings
... recognises locomotives (two out of three times)
... is not even issued ammunition
... can stay afloat if properly instructed by Mae West
... talks to walls.
2nd Lieutenant / Pilot Officer / Sub-Lieutenant
... falls over doorstep when trying to enter buildings
... says "Look at the Choo-Choo!"
... wets himself with water pistol
... plays in mud puddles
... mumbles to himself.
Sergeant-Major / Flight Sergeant / Chief Petty Officer
... lifts buildings and walks under them
... kicks locomotives off the track
... catches speeding bullets in his teeth, and eats them
... freezes water with a single glance
... he IS God.