May 1917
| Date | Events |
|---|---|
| 2 | First United States destroyer flotilla arrives at Queenstown (now Cobh) in Cork, Ireland |
| 2 | Third Battle of the Scarpe and the Battle of Bullecourt (both parts of the Battle of Arras) begin. Scarpe soon over but there is protracted fighting for Bullecourt |
| 4 | French forces recapture Craonne on the Chemin des Dames ridge |
| 5 | Battle of Vardar begins in Macedonia, lasts to 22 May |
| 7 | First night air raid on London - a single aircraft, by moonlight |
| 9 | First Battle of Doiran (now Dojran) ends in Salonika |
| 10 | Major General John J. Pershing appointed to command United States Expeditionary Force |
| 12 | Tenth Battle of the Isonzo begins |
| 14 | British warships down German airship L22 in North Sea |
| 15 | Fourteen British drifters are sunk in Straits of Otranto as British and Austrian naval forces clash |
| 15 | Major change in French command as Petain suceeds Nivelle as Commander-in-Chief of Northern and North-Eastern Army Groups and Foch succeeds Petain as Chief of the General Staff |
| 16 | Kerenski succeeds Guchkov as Russian Minister of War |
| 17 | Honduras severs diplomatic relations with Germany |
| 17 | British Admiralty appoints a committee to draw up a plan to convoy merchant shipping |
| 18 | Compulsory Service Act becomes law in United States |
| 18 | Nicaragua severs diplomatic relations with Germany |
| 19 | Russia provisional government repudiates a separate peace |
| 19 | United States government announces it will send a Division to France at one |
| 25 | Heavy casualties (290, more than half civilians) in first great aeroplane raid over England, as German aircraft bomb Folkestone and parts of Kent |
| 26 | British hospital ship "Dover Castle" sunk by submarine in the Mediterranean |
| 28 | Anglo-French conference in London discusses attitude of King Constantine of Greece and considers occuptaion of Athens and Thessaly |
| 30 | General van Deventer succeeds General Hoskins in command of British forces in East Africa |