At the beginning of the First World War, Neidholdt and his regiment were sent to the Western front, where he took part in the Siege of Namur. At the beginning of 1915, his unit was sent to fight Russian imperial forces near Bzura. Between March 1915 and April 1917 Neidholdt served at various positions at army, divisional, brigade, and company level on the eastern front. After the Reichswehr became the Wehrmacht, he retired from the army on 21 May 1935. On 1 December 1938, he returned as an officer in the army and in the spring of 1940, he led a regiment on the Western Front then commanded an infantry regiment for short time in Poland before ending up on the reserve list of the army high command.