Complex sentence: Three days later on 9 August 1945, the primary target was Kokura however, due to cloudy weather and smoke from the neighboring city of Yahata the plutonium bomb was dropped on the secondary target, the city of Nagasaki.
Split into simpler sentences: Three days later on 9 August 1945, the primary target was Kokura. However, due to cloudy weather and smoke from the neighboring city of Yahata the plutonium bomb was dropped on the secondary target, the city of Nagasaki.