Final answer:
The Blitz during World War II resulted in London being bombed extensively by Hitler's forces in an attempt to break British morale. Despite widespread destruction and civilian casualties, British industrial production continued, and the country's morale remained unbroken.
Step-by-step explanation:
The period referred to in the question, with London being bombed 20-30 times a week, is associated with The Blitz during World War II. Hitler was in anger over Britain's refusal to negotiate and, after the failure of the Luftwaffe to gain air supremacy in the Battle of Britain, initiated a bombing campaign on British cities to break the morale of the British people. This intensive bombing, beginning on September 7, 1940, targeted not only London but also other population centers and industrial cities across Britain.
The Blitz led to significant devastation and civilian casualties, with London and other cities suffering extensive damage. Despite these efforts, British morale did not break, and the country's industrial production continued, largely because it had been moved out of major cities. British defense efforts, led by the Royal Air Force, were crucial during this period, and the population was bolstered by Churchill's encouragement to 'keep calm and carry on.'