During March an average of 40 U-boats at sea per day and maximum of 57. Shipping entering British ports in February and March is only 25% of February to March 1916 levels. 16 British oilers (Fleet tankers) sunk March to September. Germany announces end of safe period for sailing ships in Atlantic.
Channel: British hospital ship Glenart Castle damaged by mine between Le Havre and Southampton. Further mine or torpedo disasters to hospital ships on March 20 (Asturias; 14 killed), March 30 (Gloucester Castle, no lives lost); April 10 (Salta, 52 killed); April 17 (Lanfranc, 35 killed including 20 Germans) and ambulance-transport (red crosses and distinctive marks dropped) Donegal (41 killed). Germans convinced hospital ships carrying munitions and radioing U-boat positions.
Mediterranean: From mid-April British hospital ships sailing zigzag course and get 2 destroyer escorts. French embark 70 German officer PoWs (April 15 to c.August 15) in 5 hospital ships and notify Berlin (which sends 200 French officer PoWs to Western Front areas shelled by Allies).
Austria: Arz succeeds Conrad as CoS.
Germany: Colonel Hentsch (Marne decision) made CoS German Rumania military occupation.
USA: Wilson hands press Zimmermann Telegram. In March DW Griffith sails for Europe to make two British-funded films on Western Front.
Switzerland: Rice and sugar rationing cards issued (2 meatless days per week since February 12).