During the First World War, while serving in the Royal Naval Volunteer Reserve, he was assigned to submarine patrols in the Dardanelles, Gallipoli and Gibraltar, and, beginning in 1917, to a minesweeping operation at HMNB Devonport. In April 1917, German submarines (called U-boats) achieved unprecedented success in torpedo attacks on British ships, sinking nearly eight per day. In his autobiography, Wilkinson remembers the moment when, in a flash of insight, he arrived at what he thought would be a way to respond to the submarine threat. He decided that, since it was all but impossible to hide a ship on the ocean (if nothing else, the smoke from its smokestacks would give it away), a far more productive question would be: how can a ship be made to be more difficult to aim at from a distance through a periscope? In his own words, he decided that a ship should be painted "not for low visibility, but in such a way as to break up her form and thus confuse a submarine officer as to the course on which she was heading".