A night bomber is a bomber aircraft intended specifically for carrying out bombing missions at night. The term is now mostly of historical significance and was especially used prior to and during World War II. A number of modern types are designed primarily for night-time bombing, but air forces no longer refer to them as night bombers. More common terms today include interdictor and strike fighter.
Prior to the introduction of radar, aircraft flying at night were nearly impossible to locate accurately enough for attack. Acoustic location was used to obtain preliminary rough coordinates. Anti-aircraft artillery scanned the sky with searchlights, which could illuminate the aircraft by chance and attempt to track it for some time. Alternatively, night fighters were used for interception; they either cooperated with searchlights or tried to spot the bombers in the moonlight. The success rate of such defences were so low that it was widely believed that "The bomber will always get through". Even since World War I, the bomber became seen as a terror weapon, and later as a primary strategic weapon of total war. As Baldwin later said, their primary purpose was to "kill the enemy's women and children more rapidly than they killed yours".
As aircraft capabilities grew, so did their defensive firepower. By the mid-1930s, opinions were changing and the idea of daylight raids of aircraft providing their own self-defence came to the fore. In practice these aircraft proved entirely vulnerable to modern fighter aircraft and were rapidly returned to the night bombing role. However, these aircraft had not been designed for night navigation, and were generally lacking any effectiveness in these missions:
I don't think we realised at the time that our equipment wasn't really up to it. They'd forgotten to design or produce any navigation equipment, so the Wellington bomber, which was intended to be a day bomber, had to operate at night because it was so vulnerable during the day. It had virtually the same equipment that the Tiger Moth had, with one exception—the Wellington had a loop aerial. Here we were flying 500 or 600 miles over enemy territory, trying to locate a target in total blackout, often with cloud below us and a lot of industrial haze. It's not surprising that our bombers were 5, 10 miles away. There was no bomber stream. We were largely on our own, perhaps 10 or 14 aircraft at intervals.
- —John Gee, Bomber Command pilot
The USAAF was the only force to press ahead with daylight strategic bombing raids during World War II. This proved as disastrous as the earlier Royal Air Force and Luftwaffe attempts, and had to be called off in late 1943. The arrival of the P-51 Mustang fighter in the "bomber escort" role allowed these missions to start again in 1944, and the fighter was so successful that the Luftwaffe fighter force was largely wiped out by the end of spring. Attrition of the Luftwaffe was so great that the RAF was also able to take to the daylight skies later that year.