In late November 1944, after returning to the U.S., Hays assumed command of the 10th Mountain Division when its CG, Major General Lloyd E. Jones, fell ill. After training, the division arrived in Italy in January and fought throughout the spring offensive. On April 24, 1945, Colonel William Darby was assigned as Hays' Assistant Division Commander, but was killed in action six days later. After the end of the war in Europe, Hays became High Commissioner for the US Occupation Zone in Germany from 1949, and assumed command of the occupation forces or U.S. Forces Austria (USFA) in April 1952, in Salzburg. He retired from the military in 1953, having reached the rank of lieutenant general.