Answer:
For British citizens to be brave in the coming war with Germany.
Step-by-step explanation:
At the start of World War II, Britain still had a large empire: the British Empire, and Churchill was the Prime Minister.
What Churchill meant with his speech was that, either in victory or defeat, facing the might of Nazi Germany was so important, and so brave, that future generations and historians would undoubtely consider that moment as the best moment in all of the British Empire history.