Task: Question Generation
Input (English): Not all of the Luftwaffe's effort was made against inland cities. Port cities were also attacked to try to disrupt trade and sea communications. In January Swansea was bombed four times, very heavily. On 17 January around 100 bombers dropped a high concentration of incendiaries, some 32,000 in all. The main damage was inflicted on the commercial and domestic areas. Four days later 230 tons was dropped including 60,000 incendiaries. In Portsmouth Southsea and Gosport waves of 150 bombers destroyed vast swaths of the city with 40,000 incendiaries. Warehouses, rail lines and houses were destroyed and damaged, but the docks were largely untouched.
Output (English): Why were port cities targeted by the Luftwaffe?