Contraband of war

The Declaration of London of 26 February 1909, agreed by ten naval powers, divided goods into three groups. Absolute contraband, meaning arms, ammunition and military equipment, could be seized on its way to the enemy, even via a neutral port. Conditional contraband, dual-use goods such as food, fuel or gold, only on its way to the enemy's forces or government and not via a neutral port. The free list included textile raw materials, rubber and ores. No one ratified the Declaration, because the British House of Lords rejected it.

In August 1914 Britain and France announced that they would apply it with their own changes. In the following months they moved goods from the free and conditional lists to the absolute one, and seized conditional contraband even on its way to neutral ports if it was bound for Germany. Neutral countries, especially the United States and the Netherlands, protested. On 7 July 1916 the Allies abandoned the Declaration, and by the end of the war almost any cargo bound for Germany was treated as contraband.