Instituted 1943 as the 1939-43 Star for 6 months of operational service between 3 September 1939 and the end of the war. In July 1998 several amendments were made, greatly expanding the numbers entitled to this medal. The people most affected will be those who had not completed 6 months of operational service at war's end in either Europe or the Pacific. 
 
Possible clasps:
1. Battle of Britain
2. Aircrew Europe