Knowing that the narrator is speaking directly to you as the reader and giving only his perception of what happened leads to questions of whether or not he is a reliable narrator and lends an air of mystery to the story. In the opening of the story he even says he does not expect to be believed and that his “senses reject their own evidence,” so the reader cannot be sure of what is true....
He is saying that England will endure WW2, even if they are losing in the moment. He is saying that if they do surrender now, England will eventually win.
It’s the planet can protect
