The main section of the novel Spies takes place probably during the summer of 1942.
Take some time to research some of the major events that took place prior to this date. There are lots of clips on youtube and elsewhere to do this research.
Here are some key words you can use as starting points for your research.
I've put a couple of links here to start you off
The Secret Seven
The Famous Five
Dunkirk 1940
The Battle of Britain
The Blitz
