Complex sentence: The Bombing of Warsaw in World War II refers both to the bombing campaign of Warsaw by the Luftwaffe during the siege of Warsaw in the Invasion of Poland in 1939 and to the German bombing raids during the Warsaw Uprising in 1944.
Split into simpler sentences: The Bombing of Warsaw in World War II refers to the bombing campaign of Warsaw by the Luftwaffe during the siege of Warsaw in the Invasion of Poland in 1939. It also may refer to German bombing raids during the Warsaw Uprising in 1944.