* Germany invades Poland (September, 1939)
* Britain, France, Canada, Australia and New Zealand declare war on Germany (September, 1939)
* Soviets invade Poland, which is later split (October, 1939)
* Nazis begin euthanasia of ill and disabled in Germany (October, 1939)
* Soviets attack Finland (November, 1939)
So by the time Orwell published his review, it was clear Germany and the Soviets were mobilizing for war, but it was entirely unclear what would happen next.
In the next six months, Germany would invade Denmark, Norway, France, Belgium, Luxembourg, and the Netherlands while beginning their blitz on Great Britain. The Soviets would take Latvia, Lithuania, and Estonia. Mussolini would meet Hitler in Munich, declare war on France and Britain and Italian forces would take Greece and enter Egypt. The Tripartite Pact would be signed by Germany, Italy, and Japan to formalize their alliance.
It's amazing to me how fast things moved during that time.