Germany: Rudolf Höss and a group of Nazi Party members murder suspected communist Walther Kadow in Mecklenburg to avenge the death of fellow party member Albert Leo Schlageter.
1933 — , May 31
CBI - China: The Tanggu Truce is signed between China and Japan to end the undeclared war between them. However, it'll take a few days for the fighting to end.
1937 — , May 31
Spain: Day 319 of 985 of the Spanish Civil War. Spanish Republicans begin an offensive to capture Segovia. Three Republican Divisions break through the Nationalist front line at San Ildefonso and capture La Granja.
1938 — , May 30
Spain: Day 684 of 985 of the Spanish Civil War.
CBI - China: Day 329 of 2,987 of the 2nd Sino-Japanese War.
Day 114 of 124 of the Battle of Henan.
1939 — , May 31
CBI - China: Day 694 of 2,987 of the 2nd Sino-Japanese War.
CBI - Mongolia: Day 21 of 129 of the Battle of Khalkhin Gol, a border dispute between the Soviet Union and Japan.
1940 — , May 31
USA: The US Ambassador to Argentina and the US Minister in Uruguay meet in Montevideo, Uruguay. They jointly request that President Roosevelt send 40 to 50 warships to South America to prevent Uruguay from joining the Axis with Germany.
Atlantic: British sloop HMS WESTON sinks the German sub U-13 with depth charges 14 miles southeast of Lowestoft, England.
Atlantic: German sub U-101 attacks an Allied convoy and sinks the British ship ORANGEMOOR.
Atlantic: Heavy Luftwaffe attacks sink two French destroyers off the beaches at Dunkirk.
ETO - Norway: Day 53 of 63 of the Battle of Norway. Allied troops continue pushing the Germans out of the Narvik region toward Sweden.
ETO - France: Day 22 of 44 of the Battle of France. The French defenses at Lille collapse. Day 5 of 9 of Britain's Operation DYNAMO, the evacuation of Dunkirk. Another 68,014 troops are evacuated to England.
CBI - China: Day 1,060 of 2,987 of the 2nd Sino-Japanese War.
Day 199 of 381 of the Battle of South Guangxi.
Day 31 of 49 of the Battle of Yichang.
1941 — , May 31
Atlantic: German sub U-69 sinks the British ship SANGARA at Accra harbor on the Gold Coast. U-38 sinks the Norwegian ship RINDA off Liberia. U-106 sinks the British ship CLAN MACDOUGALL near Cape Verde Islands. U-107 sinks the British ship SIRE off Sierra Leone, British West Africa.
Atlantic: German sub U-147 sinks the British ship GRAVELINES 100 miles northwest of Ireland, while U-204 sinks the small Icelandic fishing boat HOLMSTEINN northwest of Iceland.
ETO - Ireland: Dublin is accidentally bombed by the Luftwaffe, intending to hit Liverpool. 28 are killed and 87 are wounded. Later, Germany will offer compensation. German bombers also attack Merseyside, England.
MTO - Greece: Day 12 of 13 of the Battle of Crete. The British evacuation continues under heavy air attacks.
MTO - Libya: Day 52 of 256 of the Siege of Tobruk.
Middle East: Day 30 of 30 of the Anglo-Iraqi War in Iraq. The mayor of Baghdad surrenders to the British. As a sign of good faith, the British allow the Iraqi Army to return to their barracks and all captured equipment is returned. Both sides agree to release their captured POWs with the exception of German and Italian troops captured by the British. Iraq also agrees to support the Allies against the Axis.
East Africa: Day 356 of 537 of Italy's East African campaign in the lands south of Egypt.
CBI - China: Day 1,425 of 2,987 of the 2nd Sino-Japanese War.
1942 — , May 31
Atlantic: Day 138 of 169 of Germany's Second "Happy Time," during which U-boats sink 609 Allied ships with little risk.
Since the start of Operation DRUMBEAT (the first wave of attack by five Type IX boats immediately after war was declared on the US), U-boats have sunk 111 vessels along the US eastern seaboard.
Germany: The Monowitz labor camp, later known as Auschwitz III, opens by housing forced laborers to build the Buna-Works for the German chemical firm I G Farben.
Russian Front - North: Day 266 of 872 of the Siege of Leningrad.
Russian Front - North: Day 27 of 658 of the Siege of the Kholm Pocket.
Russian Front - Center: Day 3 of 31 of Operation KREMLIN, a German diversion to trick the Soviets into thinking Moscow is their main objective instead of Stalingrad and the Caucasus.
Russian Front - South: Day 214 of 248 of the Siege of Sevastopol, Crimean Peninsula.
MTO - Libya: Day 6 of 27 of the Battle of Gazala. The Afrika Korps begins their attack on the Gazala line.
East Africa: Day 27 of 186 of the Battle of Madagascar.
CBI - China: Day 1,790 of 2,987 of the 2nd Sino-Japanese War.
Day 17 of 124 of Japan's Zhejiang-Jiangxi Campaign, launched to punish anyone suspected of aiding the Doolittle raiders in China. Roughly 250,000 Chinese will be killed.
PTO - Australia: Day 1 of 9 of the Battle at Sydney Harbor. A Japanese midget submarine enters Sydney Harbor.
PTO - Malaya: Day 102 of 357 of the Battle of Timor Island.
PTO - New Guinea: US 5th Air Force B-17s attack at Lae and Salamaua.
1943 — , May 31
USA: Day 1 of 9 of the Los Angeles Zoot Suit Riots. Fighting erupts and escalates between young Mexican-Americans in zoot suits and thousands of white sailors asserting their racial supremacy by beating and stripping the oversized fashion from the wearers.
Zoot Suit Riots, Los Angeles, 1943 Crowd gathers around beaten and stripped Pachucos
It started when a group of some fifty sailors on leave ran amok in Los Angeles, viciously targeting and attacking Mexican-American youths wearing zoot suits. Deemed to be provocatively flaunting a lack of patriotism by wearing such flamboyant garb during wartime, the victims were stripped, beaten and even urinated upon and their oversized garb ritualistically burned.
For the next two weeks, thousands of servicemen will join in the hunt for young zooters, who were all underage youth too young to be drafted into military service. The rampaging will stop only when the army and navy commanders in southern California confine military men to their bases on June 8, 1943.
However, similar rioting will spread into other ports and urban centers such as Detroit, Chicago, Philadelphia and Harlem where African-Americans dressed in zoot suits become major targets.
Zoot Suit Riots related dates...
13 Jan 43: Sleepy Lagoon trial verdicts become precursor
31 May 43: Day 1 of 9 of the Los Angeles Zoot Suit Riots
03 Jun 43: Day 4 of 9 of the Los Angeles Zoot Suit Riots
07 Jun 43: Day 8 of 9 of the Los Angeles Zoot Suit Riots
16 Jun 43: Eleanor Roosevelt comments on the Riots
21 Jun 43: Calif looks for Nazi subversion in riots, finds none
Atlantic: Later to be known by Germany as Black May, 41 U-boats have been sunk this month in the Atlantic, due to greatly improved Allied anti-submarine techniques and tactics. The remaining U-boats are withdrawn.
ETO - Denmark: The Danish resistance blows up an engine shed at Toender as sabotage mounts, despite Danish King's appeal for a halt.
Russian Front - North: Day 631 of 872 of the Siege of Leningrad.
Russian Front - North: Day 392 of 658 of the Siege of the Kholm Pocket.
MTO - Italy: Day 10 of 20 of the naval and aerial bombardment of Pantelleria Island.
MTO - Italy: US 9th Air Force RAF heavy bombers attack oil stores, the harbor and a seaplane base at Augusta.
MTO - Italy: US 12th Air Force B-17s bomb the airfield and marshalling yard at Foggia while other planes attack at Sardinia and on Pantelleria Island.
CBI - China: Day 2,155 of 2,987 of the 2nd Sino-Japanese War.
Day 20 of 23 of the Battle of West Hubei. Troops under Chiang Kai-Shek surround three Japanese divisions on the Yangtze River. US 14th Air Force provides air support.
PTO: Day 5 of 47 adrift in a raft for the survivors of B-24 GREEN HORNET that crashed 850 miles from Hawaii.
PTO - Alaska: Day 359 of 435 of the Battle of Kiska, Aleutian Islands. US 11th Air Force attacks targets at Kiska.
PTO - New Guinea: Day 40 of 148 of the 2nd Battle of Lae-Salamaua. US 5th and 13th Air Forces provide air support.
1944 — , May 31
ETO: US 8th Air Force B-17s and B-24s hit marshalling yards and aircraft industry targets in Germany and rail targets in France and Belgium.
ETO - France: US 9th Air Force B-26s bomb highway bridges in France.
Russian Front - North: Day 120 of 191 of the Battle of the Narva Isthmus, Estonia. Both German and Soviet troops remain in their defensive positions.
Russian Front - South: Day 54 of 60 of the Battle of Romania, 1st Jassy Offensive. A German counter-attack north of Jassy is repulsed.
MTO - Romania: US 15th Air Force bombs targets in the area of Ploesti.
MTO - Italy: Day 131 of 136 of the Battle of Anzio. RAF and US Air Forces provide air support.
CBI - Burma: Day 88 of 166 of the UK's Operation THURSDAY. Monsoon season bogs down all operations in Burma.
CBI - Burma: Day 83 of 147 of the Battle of Myitkyina. US 10th Air Force provides air support. Monsoon season bogs down all operations in Burma.
CBI - Burma: Day 61 of 302 of the Chinese Salween Offensive. US 14th Air Force provides air support. Monsoon season bogs down all operations in Burma.
CBI - China: Day 2,521 of 2,987 of the 2nd Sino-Japanese War.
Day 45 of 259 of Japan's Operation ICHI-GO.
CBI - India: Day 85 of 118 of the Battle of Imphal-Kohima.
PTO - New Guinea: Day 5 of 83 of the Battle of Biak. 5th Air Force provides air support.
PTO - New Guinea: Day 169 of 597 of the Battle of New Britain. US 13th Air Force provides air support.
PTO - New Guinea: Day 40 of 481 of the Battle of Western New Guinea. 5th Air Force provides air support.
PTO - Solomon Islands: Day 213 of 295 of the Battle of the Bougainville Islands. US 13th Air Force provides air support.
1945 — , May 31
CBI - China: Day 2,886 of 2,987 of the 2nd Sino-Japanese War.
Day 61 of 91 of the Battle of Zhijiang. US 14th Air Force provides air support. Japanese troops continue pulling out of China.
Day 53 of 60 of the Battle of West Hunan (near Zhijiang). Japanese troops continue withdrawing from southern China.
Chiang Kai-Shek resigns as the Chinese Premiership, but remains as President and Generalissimo, with Dr Soong succeeding him as premier.
PTO - Dutch East Indies: Day 31 of 52 of the Battle of Tarakan Island.
PTO - Japan: Day 61 of 83 of the Battle of Okinawa.
PTO - New Guinea: Day 521 of 597 of the Battle of New Britain. US 10th Air Force provides air support.
PTO - New Guinea: Day 405 of 481 of the Battle of Western New Guinea. US 10th Air Force provides air support.
PTO - Philippines: Day 223 of 299 of the 2nd Battle of the Philippines, aka the Liberation of the Philippines or the Philippines Campaign.
PTO - Philippines: Day 168 of 244 of the Battle of Luzon. 5th Air Force provides air support.
PTO - Philippines: Day 83 of 159 of the Battle of Mindanao Island. 5th Air Force provides air support.
PTO - Philippines: Day 75 of 135 of the Battle of the Visayas region. US 5th and 7th Air Forces provide air support.
1946 — , May 31
China: Chen Cheng is relieved from his position as the head of the political bureau of the Nationalist military and is named Commander-in-Chief of the Chinese Navy and the Chairman of the Joint Chiefs of Staff.
Day-By-Day listings for May 31 were last modified on Wednesday, January 27, 2016