During World War II, several projects were undertaken at Peenemunde to mount rockets on a U-boat. In 1941 first trials were held, using a Nebelwerfer rocket launcher, mounted on the deck of U-511. Tests were carried out, with successful firings from the surface, and from up to 12 metres underwater without any effect on the missiles' accuracy. The arrangement was envisaged as a weapon against convoy escorts, but with no guidance system the arrangement was largely ineffective.