It started on the 1 of September 1939 when Hitler invaded Poland.
It ended in 1945 when the Axis powers surrendered and Hitler committed suicide.
The British government was worried that a new war might begin when Hitler came to power in 1933. They were afraid that British cities and towns would be targets for bombing raids by aircraft.Evacuation tried to ensure the safety of young children from the cities that were considered to be in danger of German bombing - London, Coventry, Birmingham, Portsmouth etc.
Air raid shelters are for people who are not part of the war to be safe