With the advent of aircraft being able to drop bombs on enemy targets in World War I, every country with a burgeoning fleet of bombers struggled with dropping bombs on target. By World War II, the combatants resorted to sending hundreds (and later in the war, thousands) of bomber aircraft over a target with the hope that a few bombs would score a lucky hit on the intended target. It was common for bombs to miss the intended target by miles! The problem was so pervasive, that British Bomber Command's strategy throughout the war was to simply target entire cities, the logic being that even bombs that miss by miles would surely still hit somewhere in the city. British Bomber Command measured its success essentially on how many German cities that it leveled. Such was British strategy that Bomber Command focused its efforts on nighttime bombing raids since the pilots and bombardiers didn't really need to see their target - the target city was below them somewhere, their exact position over the city was quite irrelevant.
The United States Army Air Corps (it was not yet called the United States Air Force) took a different approach. The U.S. believed that it could pick specific targets for ariel bombardment, such as factories, rail yards, refineries, etc. In theory, such a strategy has no downsides since fewer bombs means less men being put at risk, less material being expended and less collateral damage. But how did the U.S. intend to accomplish this strategy when bombs were missing by miles? It doesn't take much of an imagination to understand how difficult it is to drop a bomb from an aircraft moving at several hundred miles per hour, from an altitude of several thousand feet, through a turbulent atmosphere on to a target that more often than not is protected by anti-aircraft guns and pumping thousands of exploding shells into the path of the bombers.
Enter Carl Norden.
Norden was Dutch and was born in 1880 in what is now Indonesia. He earned a mechanical engineering degree from the Zurich Federal Polytechnic School in Switzerland. He immigrated to the U.S. in 1904 and worked for the Sperry Gyroscope Company, where he gained valuable experience with gyrostabilizers and gyrocompasses. After forming his own company, he began working on a new bombsite. His instrument (essentially an analog computer with a gun site) accounted for the altitude, speed and drift of the aircraft, but more importantly told the bombardier when to drop the bombs. In controlled tests, bombers were able to drop bombs within several hundred feet of their target from altitudes in excess of 15,000 feet - an almost unbelievable achievement.
The U.S. military was so enthralled with the Norden bombsite that the highest level of secrecy and security surrounded its development, manufacture and use, particularly once war broke out. Bodyguards accompanied Norden. The factory was closely guarded. The bombsite was to be covered at all times unless installed in a bomber that was about to takeoff on a mission. Bombardiers swore oaths to destroy any bombsite that might fall into enemy hands (the bombsite itself contained small thermite charges designed to melt the instrument if necessary).
Although the use of the Norden bombsite in combat never matched the accuracy seen in the controlled tests, most experts agree that its use led to a level of accuracy unheard of before and was a significant contributing factor in the Army Air Corps' strategy to conduct daylight raids on specific targets throughout the war. To put into perspective how important the U.S. government saw the Norden bombsite, it spent 1.5 billion dollars in its development, half as much as the entire Manhattan Project to develop the atomic bomb.
All of this, from an immigrant who came to the U.S. to help us win a war.