Some targets are pretty obvious, such as the Ploesti oil fields, the submarine pens at Lorient and St. Nazaire, the Bremen ship yards, and the railyards connecting France and Germany. All of these represented targets whose purpose was indisputably assisting the German war effort. Other targets, however, may be obvious to those familiar with engineering, but not for the average historian.

The first and most historically significant is Schweinfurt. Any bomber crewman who was lucky enough to survive either of those bombing missions would never forget it for the rest of their lives. The first mission, which took place on August 17th, 1943, resulted in the loss of 60 bombers, with a further 70 returning with extensive damage, out of an original force of 376. The second mission, 2 months later, had similar results. Overall, this may seem like a small fraction of losses (16%), but you should consider that some bomber groups suffered more damage than others. In fact, the 381st bomber group sent 20 bombers on the raid, while only 11 came back. Imagine coming home from a mission where half of your squadron mates are dead....

So what was so important about Schweinfurt? This city was home to a large concentration of factories that produced ball bearings, which are necessary in almost every mechanical engineering application you could think of. Ball bearings allow machines and mechanical objects to rotate freely upon an axis, so nearly everything with an engine or a wheel requires them. Thus, the Allies were eager to take the factories out of service to hinder the German war effort.

Sometimes, mission planners weren't quite sure what they were sending their men to bomb, and only realized after the fact how important their target really was. An example of this was the bombing raids on Peenemunde, which were the testing grounds for the V-1 and V-2 rockets. Allied planners received [photo reconnaissance] (http://1.bp.blogspot.com/-p-83Nchocto/Udtjl7FKVPI/AAAAAAAAYbg/Q7MsV3-oo5U/s1600/bombed%2BV1%2Brocket%2Bsite.jpg) of the factories, but had no idea what was actually being produced. They only realized that it was a possible V-1 launch/test site when they recognized the long lines of scorched earth in the ground (you can make out one near the bottom left corner of the big square building) which was confirmed later by [photo reconnaissance] (http://upload.wikimedia.org/wikipedia/commons/5/5c/Peenemunde_test_stand_VII.jpg). The RAF and USAF compared these photographs with reconnaissance photographs of the French countryside, and found similar burn marks on the ground. Thus, mission planners were able to deduce that these sites represented crude launching grounds for the V-1's, and a resulting bombing campaign focused on those sites. This campaign became known as Operation Crossbow after the war.