Hiroshima and Nagasaki were chosen for several reasons. First, both cities were unsuitable for firebombing, mainly due to the river deltas preventing firestorms from being very effective. Second, both cities had areas which provided a good measurement for damage caused by the nuclear bombs. Third and finally, both cities contained strategic personnel and installations; Hiroshima was the headquarters of the 2nd General Army and 5th Division with 40,000 Japanese combatants stationed within the city's limit, and Nagasaki contained two large Mitsubishi armament factories and many other medium-to-small workshops and plants providing vital war components for Japan's war machine.