What did winston churchill vow to the british people after the evactution of dunkirk?

"WE SHALL NEVER SURRENDER"

Explanation:

On 10 May 1940, Winston Churchill became the prime minister of Great Britain, the first crisis he had to deal with was Dunkirk 1940.Britain was all alone in Europe as Nazi Germany conquered most of the mainland of Europe.It was the darkest hour for great Britain, Churchill had to make people believed that the war was not over not lost, Britain should prepare for the threat of Nazi's aggression.Churchill made a famous speech, his speech included phrases like We shall never surrenderwe shall fight them on the beaches this speech reflects his determined position.  

An elector in the electoral college.