Galicia – AUSTRO-GERMAN OFFENSIVE: BATTLE OF GORLICE-TARNOW (until May 5) starts with 610 gun bombardment including gas shells.
Baltic Provinces: Lauenstein occupies Shavli and nears Libau (taken seven despite checks south of Mitau on May 5).
Carpathians: Austro-German attack towards Uzsok Pass.
In May German Army has 171 divisions (figures for June 1916 are 172 or 173) with 106 in the West. French Army combatant strength 1,525,000 infantry; 102,000 cavalry; 395,000 gunners; 104,000 engineers; 8,000 air service.
During May British Mills Bomb grenade first issued as ‘Grenade Hand, No 5’.
Meuse-Argonne: Small-scale but almost continuous trench warfare in the Woevre woods until June 20.
Ypres: Gas attack on Hill 60 fails. British begin withdrawal to new line until May 4 after French counter-attack fails.
Champagne: In May African explorer General Marchand put in command of elite 10th Colonial Division which he commands for duration being twice.
Serbia: From May (to September) Major Primavesi of Austrian Intelligence begins finding whole Serb Army by means of questions inserted in Red Cross letters to PoWs in Austria. Austrians reduce forces in theatre by 5 divisions (partially replaced by 3 newly forming German ones).
Germany: Italian military attaché in Berlin deliberately allowed to see two Hindenburg letters, one saying he will command against Italy, other contemptuous of her.
Gallipoli – Helles bridgehead: 29th Indian Brigade landing, vain Turk night attack.
Persia: Nazarbekov forces 10,000 Turks north of Dilman over frontier.
Cameroons: Allied advance on Yaunde begins in heavy rain.
Southwest Africa: South African troops occupy Kubas, take Otimbingwe next day.
First US merchant ship torpedoed without warning: by U30 sinks SS Gulflight off Scilly Islands, 3 people die.
North Sea: 4 Harwich Force destroyers sink 2 German torpedo boats (42 survivors). U16 sinks destroyer Recruit off Galloper lightship.
Germany: In May 10 new UE-type oceangoing minelaying U-boats with 5.9-in gun ordered (launched from June 16).
Britain: In May Royal Navy able to track U-boats to within c.20nm either beam. During May 11 monitors launched, 9 completed in June.
Dardanelles: British submarine E14 sinks Turk gunboat in Sea of Marmara (E11 too, on May 23) and 5,000t transport Guj Djemal (on May 10) with 6,000 troops and artillery battery north of Kalolimno Island. E14 returns on May 18, Commander Boyle awarded Victoria Cross.
French submarine Joule mined and lost with all hands.
France: In May De Goys and Happe activate first French and Allied strategic bomber group GBI.
Britain: In May 500 men on waiting list for Royal Flying Corps commissions.
China: Government requests Tsingtao’s return by Japan.
USA: U-boat torpedoes US tanker Gulflight off Scilly Islands, 3 people die. Germany apologizes on June 1.
Austria: 2nd War Loan.