World War Two in Europe began on 3rd September 1939, when the Prime Minister of Britain, Neville Chamberlain, declared war on Germany. It involved many of the world's countries.
The Second World War was started by Germany in an unprovoked attack on Poland. Britain and France declared war on Germany after Hitler had refused to abort his invasion of Poland.
The heavy and frequent bombing attacks on London and other cities was known as the 'Blitz'. Night after night, from September 1940 until May 1941, German bombers attacked British cities, ports and industrial areas.
London was bombed ever day and night, bar one, for 11 weeks. One third of London was destroyed.
The first German air attack took place in London on the evening of 7 September 1940. Within months, Liverpool, Birmingham, Coventry and other cities were hit too.