Searchlight

A searchlight (or spotlight) is an apparatus that combines an extremely bright source (traditionally a carbon arc lamp) with a mirrored parabolic reflector to project a powerful beam of light of approximately parallel rays in a particular direction. It is usually constructed so that it can be swiveled about. The most common element used in modern searchlights is xenon (Xe). However, rare-earth elements such as lanthanum (La) and cerium (Ce) are used in phosphors to improve light quality in some specialized searchlights.

The first use of searchlights using carbon arc technology occurred during the Siege of Paris during the Franco-Prussian War. The Royal Navy used searchlights in 1882 to dazzle and prevent Egyptian forces from manning artillery batteries at Alexandria. Later that same year, the French and British forces landed troops under searchlights.

By 1907 the value of searchlights had become widely recognized. One recent use was to assist attacks by torpedo boats by dazzling gun crews on the ships being attacked. Other uses included detecting enemy ships at greater distances, as signaling devices, and to assist landing parties. Searchlights were also used by battleships and other capital vessels to locate attacking torpedo boats and were installed on many coastal artillery batteries for aiding night combat. They saw use in the Russo-Japanese War from 1904–05.

Searchlights were installed on most naval capital ships from the late 19th century through WWII, both for tracking small, close-in targets such as torpedo boats, and for engaging enemy units in nighttime gun battles. The Imperial Japanese Navy especially was known for its intensive development of nighttime naval combat tactics and extensive training. The War in the Pacific saw a number of nocturnal engagements fought by searchlight, particularly the Battle of Savo Sound at Guadalcanal. Although searchlights remained in use throughout the war, the newly developed radar proved to be a far more effective locating device, and Japanese radar development lagged far behind that of the US.

Searchlights were first used in the First World War to create "artificial moonlight" to enhance opportunities for night attacks by reflecting searchlight beams off the bottoms of clouds, a practice which continued in the Second World War. The term "artificial moonlight" was used to distinguish illumination provided by searchlights from that provided by natural moonlight, which was referred to as "movement light" in night-time manoeuvers. Searchlights were also heavily used in the defense of the UK against German nighttime bombing raids using Zeppelins.

Searchlights were used extensively in defense against nighttime bomber raids during the Second World War. Controlled by sound locators and radars, searchlights could track bombers, indicating targets to anti-aircraft guns and night fighters and dazzling crews.

Searchlights were occasionally used tactically in ground battles. One notable occasion was the Red Army use of searchlights during the Battle of the Seelow Heights in April 1945. 143 searchlights were directed at the German defence force, with the aim of temporarily blinding them during a Soviet offensive, begun with the largest artillery bombardment the world had ever seen until that point. However, the morning fog diffused the light and silhouetted the attacking Soviet forces, making them clearly visible to the Germans. The Soviets suffered heavy losses as a result and were forced to delay their invasion of the city.

Second World War-era searchlights include models manufactured by General Electric and by the Sperry Company. These were mostly of 60 inch (152.4 cm) diameter with rhodium plated parabolic mirror, reflecting a carbon arc discharge. Peak output was 800,000,000 candela. It was powered by a 15 kW generator and had an effective beam visibility of 28 to 35 miles (45 to 56 km) in clear low humidity.