What impact did Adolf Hitler have on war?

Adolf Hitler significantly altered the course of warfare during World War II through his aggressive expansionist policies and the implementation of total war strategies. His leadership led to the rapid militarization of Germany and the invasion of numerous countries, which sparked a global conflict that resulted in unprecedented destruction and loss of life. Additionally, Hitler's ideologies, including the pursuit of racial purity, influenced the war's brutal tactics, such as the Holocaust, which aimed at exterminating entire populations. His defeat ultimately reshaped international relations and led to the establishment of the United Nations in an effort to prevent future global conflicts.