A dive bomber is a bomber aircraft that dives directly at its targets in order to provide greater accuracy. In doing so the aircraft decreases the time it takes for the bomb to reach its target, both through greater speed and shorter distance, thereby making the effects of drag and gravity less pronounced and the path of the bomb much more predictable. This allows a dive bomber to accurately place bombs on small targets with relative ease, and these aircraft were widely used to attack high value targets such as ships and bridges.
The first recorded use of dive bombing was an ad-hoc solution by RAF pilots during World War I. During 1917 and 1918 they practiced the technique at the Orfordness Bombing Range, but the aircraft of the day were generally too frail to be able to withstand the g forces generated when pulling out of the dive after releasing the bombload. Only a few years later US Marines nevertheless put the system to use in Haiti and Nicaragua.
As planes grew in strength and load capability, the technique became more valueable. By the early 1930s the technique was clearly of great value, notably against targets that would otherwise be too small to hit with level bombers. While the USAAC concentrated on mass attacks by very large bombers, the US Navy ordered the first custom dive bomber aircraft, the Curtiss F8C Hell-Diver.
In the early 1930s, Ernst Udet visited the US and was able to purchase four F8C's and ship them to Germany. There they caused a minor revolution. The dive bombing technique would allow a much smaller Luftwaffe to operate effectively in the tactical role, and this was all they were interested in. Soon they had sent out contracts for their own dive bomber designs, resulting in the Junkers Ju 87 Stuka.
For its day the Stuka was the most advanced dive bomber in the world. Using it as "aerial artillery" solved a major problem in the concept of Blitzkrieg; how to attack dug-in defensive positions. Normally this would require slow-moving artillery to be used, making the fast moving armored forces wait for it to catch up. However with the Stuka the battle could be kept moving at all times.
This was proven to great effect during the invasion of Poland and the Low Countries. In one particular example the BEF set up strong defensive positions on the west bank of the Oire River just front of the rapidly advancing German armor. Attacks by Stukas quickly broke the defense, and combat engineers were able to force a crossing long before the artillery arrived.
The Stuka soon grew outdated, but repeated efforts to replace it with a newer and more capable plane all failed. By the start of the Battle of Britain it was already hopelessly outclassed, and suffered stiffly at the hands of the RAF.
The Japanese also spent considerable effort on dive bombers, for the same reason as the US Navy – to allow it to strike ships. They started the war with one of the best designs, the Aichi D3A, but this design also quickly became outdated. They later introduced the much better Yokosuka D4Y Suisei, but at a time when their industry was already unable to supply them in any numbers. In contrast the US fielded the Douglas SBD Dauntless which was similar to the D3A in performance, but later replaced it with the somewhat better Curtiss SB2C. Both were provided in huge numbers.
Oddly the only major force not to deploy a dedicated dive bomber were the inventors, the British. The Royal Navy attempted to introduce their own on several occasions, but were never able to do so due to various reasons, not the least of which was political interference by the RAF.
After the war the dive bomber class quickly disappeared. Aircraft speeds had increased so much that the concept of diving to add more speed was becoming somewhat suspect. At the same time the quality of various computing bombsights allowed for much better accuracy from smaller dive angles, and could be fitted to almost any plane. Although the aircraft still "dove" on their targets to some degree, these same aircraft were capable of many other missions as well and were no longer considered to be dive bombers.
Today smart bombs have made all such effort largely unnessesary. Bombs can be dropped many miles from the target at high altitudes, placing the aircraft at little risk. The bomb then guides itself onto the target, either with a laser designator "painting" it, or in more modern systems, onboard GPS systems that allow the plane to leave for home. Bombsights continue to supply several "toss" modes, but are typically used only when the target location isn't known in advance, and a dive is needed to locate it.