Complex sentence: This provocation was the best-known of several actions in Operation Himmler, a Nazi Germany SS project to create the appearance of Polish aggression against Germany, which would be used to justify the subsequent invasion of Poland.
Split into simpler sentences: This provocation was the best-known of several actions in Operation Himmler, a Nazi Germany SS project. It was intended to create the appearance of Polish aggression against Germany in order to justify the subsequent invasion of Poland.