CBI - China: Day 8 of 154 of the Japanese Invasion of Manchuria.
1936 — , September 25
Spain: Day 71 of 985 of the Spanish Civil War.
1937 — , September 25
Spain: Day 436 of 985 of the Spanish Civil War.
CBI - China: Day 81 of 2,987 of the 2nd Sino-Japanese War.
Day 44 of 106 of the 2nd Battle of Shanghai.
Day 25 of 70 of the Battle of Taiyuan.
1938 — , September 25
USA:20,000 people attended a demonstration at New York Madison Square Garden to support Czechoslovakia.
Spain: Day 801 of 985 of the Spanish Civil War.
CBI - China: Day 446 of 2,987 of the 2nd Sino-Japanese War.
Day 107 of 139 of the Battle of Wuhan.
1939 — , September 25
Atlantic: German U-48 sinks the steamer ROYAL SCEPTRE and casts its crew adrift 300 miles from land.
Poland: Day 25 of 36 of Germany's Invasion of Poland. Luftwaffe bombs Warsaw with 420 planes. Casualties there have now reached 40,000 dead.
Poland: Day 9 of 20 of the USSR's Invasion of Poland.
CBI - China: Day 811 of 2,987 of the 2nd Sino-Japanese War.
Day 13 of 26 of the 1st Battle of Changsha.
1940 — , September 25
USA: Cryptanalyst Harry L Clark discovers the key to the mechanism used to encode and decode Japanese top secret messages, allowing the Allies to begin developing duplicate machines to quickly read diplomatic traffic.
Fragment of an actual Purple machine from the Japanese embassy in Berlin, obtained by the US after the war
The Japanese cipher machine code-named PURPLE, cracked by the US prior to WWII, was so complex that even the Germans were unable to decode messages sent through it.
Japan's most secret diplomatic messages were encrypted with the Purple cipher machine, which was similar in concept to the German Enigma, but used stepping switches similar to a telephone dial instead of rotors.
Harry L Clark correctly guessed that the Japanese device used stepping switches, which eventually led to successful decryption. As with the Enigma, the Allies built duplicate machines and the impact their code reading abilities had became immeasurable, making ULTRA, as it would be called, a secret weapon of enormous importance.
Dates related to cryptology...
14 Mar 40: First "Bombe" decipher machine becomes operational
22 May 40: Bletchley Park cryptologists break Luftwaffe Enigma code
25 Sep 40: US discovers key to Japanese coding mechanism
09 May 41: British capture Enigma machine and code book intact
19 Jul 41: Churchill shares Enigma findings with Soviets
19 May 42: US decodes Japanese messages regarding mysterious "AF"
30 Jun 42: British completely crack the Enigma code
13 Apr 43: Decrypted Japanese code leads to plot to kill Admiral Yamamoto
07 Aug 44: IBM dedicates first program-controlled calculator
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The Code Book: The Science of Secrecy from Ancient Egypt to Quantum
Colossus: The secrets of Bletchley Park's code-breaking computers
Skis Against the Atom: The Exciting, First Hand Account of Heroism and Daring Sabotage During the Nazi Occupation of Norway
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East Africa: Day 108 of 537 of Italy's East African campaign in the lands south of Egypt.
West Africa: Free French invasion forces, landed by Royal Navy ships, are repulsed by Vichy French troops at Dakar, French West Africa. Dakar is now the capital of Senegal.
CBI - China: Day 1,177 of 2,987 of the 2nd Sino-Japanese War.
Day 316 of 381 of the Battle of South Guangxi.
Day 37 of 42 of the Hundred Regiments Offensive.
CBI - Indochina: Day 4 of 5 of the Japanese invasion of Vichy French Indochina.
CBI - Indochina: Day 4 of 4 of the Battle of Lang Son.
CBI - Indochina: Day 2 of 3 of the Battle of Hai Phong.
1941 — , September 25
Russian Front - Finland: Day 96 of 164 of the Battle of Hanko. The Soviets will be forced off their leased naval base.
Russian Front - Finland: Day 22 of 28 of Finland's reconquest of East Karelia in southern Finland. The Soviets continue withdrawing from Finland back to Leningrad.
Russian Front - Finland: Day 89 of 142 of Operation SILVER FOX, a joint German-Finnish campaign to capture the Russian port of Murmansk in the Arctic. The German troops continue withdrawing back into northern Finland.
Russian Front - Finland: Day 87 of 140 of Operation ARCTIC FOX, a joint German-Finnish campaign against Soviet Northern Front defenses at Salla, Finland.
Russian Front: Day 96 of 167 of Germany's Operation BARBAROSSA, the overall invasion of the USSR.
Russian Front - North: Day 18 of 872 of the Siege of Leningrad. Hitler puts an end to attacking Leningrad ordering the city to be besieged and starve them out. He also ordered that after its foreseen surrender that the entire city to be leveled.
Russian Front - South: Day 49 of 70 of the Siege of Odessa, Ukraine.
Russian Front - South: Day 34 of 35 of the 1st Battle of Kiev, Ukraine. Battle comes to an end as the Soviets begin evacuating the city.
MTO - Libya: Day 169 of 256 of the Siege of Tobruk. Rommel, having discovered he had been given bad intelligence, withdraws his 21st Panzer Division back to the Libyan-Egyptian border.
East Africa: Day 473 of 537 of Italy's East African campaign in the lands south of Egypt.
CBI - China: Day 1,542 of 2,987 of the 2nd Sino-Japanese War.
Day 20 of 33 of the 2nd Battle of Changsha.
1942 — , September 25
ETO - Norway: RAF Mosquitos make a successful low level daylight raid on the Gestapo HQ in Oslo.
Russian Front - North: Day 383 of 872 of the Siege of Leningrad.
Russian Front - North: Day 144 of 658 of the Siege of the Kholm Pocket, USSR lays siege to the Kholm Pocket but the Germans hold out for a about a year and a half.
Russian Front - Center: Day 58 of 64 of the 1st Battle of Rzhev-Sychevka, Russia. Though it will end in a stalemate, it will keep German troops from going to Stalingrad.
Russian Front - South: Day 90 of 150 of Germany's CASE BLUE, the failed offensive to take the Caucasus oil fields.
Russian Front - South: Day 34 of 165 of the Battle of Stalingrad, the bloodiest battle in human history.
MTO - Libya: US B-24s attack Benghazi.
East Africa: Day 144 of 186 of the Battle of Madagascar.
CBI - China: Day 1,907 of 2,987 of the 2nd Sino-Japanese War.
PTO - Alaska: Day 111 of 435 of the Battle of Kiska, Aleutian Islands. The US and Canada will defeat the Japanese invaders.
PTO - Malaya: Day 219 of 357 of the Battle of Timor Island, a long guerrilla war ending in Japanese victory.
PTO - New Guinea: Day 67 of 119 of the Battle of the Kokoda Track. The Australians continue pushing back the Japanese troops. This will become an Allied victory.
PTO - Solomon Islands: Day 50 of 187 of the Battle of Guadalcanal.
1943 — , September 25
ETO: US 8th Air Force: B-26s hit one airfield in France.
Russian Front - North: Day 748 of 872 of the Siege of Leningrad.
Russian Front - North: Day 509 of 658 of the Siege of the Kholm Pocket, USSR lays siege to the Kholm Pocket but the Germans hold out for a about a year and a half.
Russian Front - Center: Day 50 of 57 of the 2nd Battle of Smolensk, Russia. The Soviets capture Smolensk and Roslavl, over 200 miles west of Moscow.
Russian Front - Center: Day 40 of 48 of the Battle of Bryansk, Russia. German troops continue evacuating Bryansk.
Russian Front - South: Day 33 of 122 of the Battle of the Lower Dnieper River, USSR.
MTO - Italy: The RAF, US 9th and 12th Air Forces provide the air cover for the Allied ground troops.
CBI - China: Day 2,272 of 2,987 of the 2nd Sino-Japanese War.
PTO - New Guinea: Day 7 of 219 of the Battle of Shaggy Ridge. This will become an Allied victory.
PTO - New Guinea: Day 4 of 162 of the Battle of the Huon Peninsula. This will result as an Allied victory.
PTO - Solomon Islands: Day 42 of 56 of the Battle of Vella Lavella. The Allies will win this one.
1944 — , September 25
ETO - France: Day 56 of 284 of the Battle of Brittany.
ETO - Belgium: Day 24 of 62 of the liberation of Belgium. The Canadians begin an all-out attack on the German stronghold at Calais, France.
ETO - France: Day 11 of 236 of the Siege of Dunkirk.
ETO - Netherlands: Day 9 of 9 of Operation MARKET GARDEN. The British evacuate the remaining paratroopers at Arnhem, but only 2,163 men out of nearly 10,000 are able to return. The operation has failed. Allied hopes of ending the war by Christmas are dashed.