Royal Navy painter dazzled U-boats with stripes

By 1917, German U-boats were sinking Allied merchant shipping faster than it could be replaced, and the standard naval camouflage doctrine of the era — paint a ship a low-contrast grey to blend into sea and sky — assumed concealment was the goal. Against a submarine that had already sighted a ship and was tracking it through a periscope from a few hundred yards, that assumption didn't hold: a large, slow merchant vessel on open water cannot actually be hidden once spotted, no matter what color it's painted.

Norman Wilkinson, a marine painter serving as a Royal Navy lieutenant, worked out in spring 1917 that a U-boat commander's torpedo shot wasn't aimed at where the ship was — it was aimed at where the ship would be, calculated from a brief visual estimate of its speed, heading and range through the periscope. If invisibility was off the table, corrupting that estimate directly was still available.

Painted bold stripes to break up the outline, corrupting the commander's quick periscope estimate so torpedoes aimed at a miscalculated future position missed.

Dazzle stripes broke up the ship's outline, making periscope estimates of heading and speed unreliable.

Torpedoes aim at a predicted future position, so a corrupted estimate causes a miss.

The ship stayed visible but was aimed at wrongly, so concealment wasn't needed.

When concealment is impossible, attack the attacker's measurement, not your visibility.

By the war's end more than 2,300 British merchant ships had been painted in dazzle schemes, and when the US Navy adopted the technique in 1918 it camouflaged roughly 1,256 vessels between March and November that year; of 96 US ships over 2,500 tons sunk in that period, only 18 were dazzle-painted, all merchant vessels, and none of the camouflaged fighting ships were lost.