A searchlight is a device that has a powerful light source and a concave mirror that focuses light in a particular direction for long-range illumination and search. Larger light intensities can be achieved by focusing the exiting beam in a small solid angle (typically less than 2 degrees) by means of a mirror or lens. Considering the size, weight and convenient operation of the device, it is suitable for mobile lighting in areas such as power communication and rescue, criminal investigation, work inspection, patrol, and construction engineering.

The military use of searchlights began in the 19th century. During the Japanese-Russian war, both naval warships used searchlights to search for enemy small torpedo boats at night. Searchlights are also common in coastal anti-aircraft artillery positions and air defense units. One time, John Frederick Charles Fuller used the searchlights for the first time to create the so-called "artificial moonlight" to assist in the night battle. The same tactics were used in the Second World War.

The searchlights of the Second World War have been used extensively against night air raids against the enemy. At that time, the anti-aircraft artillery used two searchlights at the same time. From the elevation angle of the searchlight, the triangulation function could be used to calculate the true height of the enemy bomber, and then used to set the anti-aircraft bullet tube to achieve the maximum effect. Searchlights can also cause considerable interference with bombers using optical bombing sights.

During the Second World War, the searchlights manufactured by General Electric used a gyro ceremony lamp holder, a 152.4 cm diameter plated concave mirror, a peak output of 800 million watts of carbon arc light source, a dedicated 15 kW generator, and an effective photo. The distance can reach 45 to 56 kilometers.