Answer the following question: Given the following passage  "Five nights later, Birmingham was hit by 369 bombers from KG 54, KG 26, and KG 55. By the end of November, 1,100 bombers were available for night raids. An average of 200 were able to strike per night. This weight of attack went on for two months, with the Luftwaffe dropping 13,900 short tons (12,600 t) of bombs. In November 1940, 6,000 sorties and 23 major attacks (more than 100 tons of bombs dropped) were flown. Two heavy (50 short tons (45 t) of bombs) attacks were also flown. In December, only 11 major and five heavy attacks were made.",  answer the following question. Note that the answer is present within the text.  Question: How did the attacks occur?
Answer:
night raids