During 1937, European tension over Mediterranean shipping grew as a result of German and Italian involvement in the war. A German vessel, The Deutschland, was thought to be carrying supplies for the Nationalists. Two Russian pilots, Captain Anton Progrorin and Lieutenant Vassily Schmidt, dropped their bombs on the Deutschland, causing severe damage on the ship and killing 31 sailors. The following day German forces bombed the Republican held city of Almeria to repress Republican air attacks on the Deutschland. The bombardment killed 19 and destroyed 35 buildings. Germany and Italy demanded that the Non-Interventionist Powers should investigate the attack on the Deutschland. Following the incident, Germany and Italy refused to recognize the 'neutrality patrol' that the Non-Intervention Committee had organized off the Spanish coast to prevent supplies from reaching Spain. As a result, France considered supporting the republicans.
Around the same time as the incident, British ships were attacked by submarines of unknown origin in the Mediterranean. On September 10, 1937, a conference was held to discuss the situation. It was decided that the Western Mediterranean was to be divided into separate patrol zones. Nine different countries, including Italy, agreed to share the supervision of the zones. Relations improved even more when Mussolini agreed to withdraw all his troops from Spain at the end of the war in the Anglo-Italian agreement of April 1938.