Complex sentence: Through the entire conflict of World War II, the Chitauri were being driven out of their operations in Africa and Europe, even from their main Japanese training camps in Hiroshima and Nagasaki.
Split into simpler sentences: Through the entire conflict of World War II, the Chitauri were being driven out of their operations in Africa and Europe. And even from their main Japanese training camps in Hiroshima and Nagasaki.