The British Air Force initially aimed to attack cities, as mentioned in a British Air Staff paper in September 1941, the purpose was to break the morale of a city's residents by making these places physically inhabitable and creating a sense of constant danger among them.
The US Air Force applied a strategy called "precision bombing" in which they would target locations of high logistic importance to the German Army. These sites included shipyards, railroads, power plants, steel mills, among others.