Any military technology intended to make vehicles or missiles nearly invisible to enemy radar or other electronic detection. Research in antidetection technology began soon after radar was invented. In World War II the Germans coated their U-boat snorkels with radar-absorbent material. By the end of the 20th century the U.S. had developed models of stealth technology, including the F-117 Nighthawk fighter-bomber and the B-2 Spirit strategic bomber. The aircraft featured surface materials and coatings that absorbed radar transmissions, faceted or rounded surfaces that reduced radar reflections, and shielded engine exhausts that reduced infrared radiation. Stealth technology has also been incorporated into the design of naval submarines and surface vessels.