All Hands Online : Official Magazine of the U.S. Navy

This was no passing trend, like bell-bottom pants and leisure suits. Whether it was a zebra-striped ship or one painted to delight a Virginia Tech fan, there was a purpose to the pattern: fooling U-boats. Known as Razzle Dazzle, the paint patterns helped safely transport troops and equipment across the Atlantic during World War I.As a young boy, Jim Bruns was fascinated by a savings bond poster that depicted a wildly painted destroyer shelling a German submarine. The destroyer was decked out in orange, blue, yellow and fluorescent red colors.”That could never be,” he thought. “At first I thought the artist had taken liberty with the colors, but then I learned about Razzle Dazzle and how it worked,” Bruns said recently. He is now the director of the National Museum of the United States Navy at the Washington Navy Yard and he knows all about “Razzle Dazzle.”

Source: All Hands Online : Official Magazine of the U.S. Navy

Back in the day, all rangefinding and target motion analysis was done via optics. Disruptive patterns were especially effective against submarines. Sub periscopes, of necessity, had very small apertures, and only dared expose themselves for brief periods. Any error introduced could easily lead to a missed torpedo shot.

The schemes didn’t work, however, very well to protect against aircraft. That’s largely why in WWII, you tended to see more dazzle paint jobs in the Atlantic, where the primary threat was the German U-Boat, and a less dramatic slate blue in the Pacific, where airplanes and surface ships were the prime threat.