Answer:
The literary work this is based on is not attached.
However, I shall answer based on historical events.
In his quest to control Europe, Hitler initiated the Battle of Britain which severely affected the British. The British were however victorious in the end due to some rash decisions by Hitler and the sheer resilience of the British Royal Air force.
Hitler then switched his attention to Russia and unleashed a devastating attack on them that pushed the Russians so far back that Russia was on the verge of collapse.
However, this attack on Russia gave Britain the much needed breathing space to reorganize her forces and everyday that Britain wasn't attacked gave them even more time to do so until they were able to launch attacks on the German army starting in Africa and then moving to Europe.