Complex sentence: After the Armistice the 8th Infantry became part of the American occupation forces in Germany until August 1919 and the remainder returned to the United States in January 1919, after which the division disbanded.
Split into simpler sentences: After the Armistice the 8th Infantry became part of the American forces in Germany until August 1919. The remainder returned to the United States in January 1919 and the division disbanded.