Nazi Germany declared war for a variety of reasons. Firstly, Hitler had always been determined to conquer Europe and had been making plans for an invasion for many years. Secondly, Hitler was paranoid about the prospect of a two-front war and was keen to avoid fighting a war on two fronts. Thirdly, Hitler was concerned about the growing strength of the Soviet Union and was keen to defeat them before they became too powerful. Finally, Hitler was influenced by a number of his advisors who were urging him to take action against the Allies.