Two further 1,000 bomber raids were executed over Essen and Bremen, but to less effect than the destruction at Cologne. The effects of the massive raids using a combination of blockbuster bombs and incendiaries created firestorms in some cites. The most extreme examples were caused by the bombing of Hamburg in Operation Gomorrah (45,000 dead), and the bombings of Kassel (10,000 dead), Darmstadt (12,500 dead), Pforzheim (21,200 dead), Swinemuende (23,000 dead), and Dresden (25,000 dead).