During the Polish campaign, Back was awarded the braces for his Iron Crosses. He then returned to the 1st Battalion, of which he had been commander the year before. In the spring of 1940 he led the 1st Battalion through Belgium and France in the western campaign, and received the Knight's Cross of the Iron Cross in August, days later being reassigned to the 304 Rifle Regiment. He won the previous Iron Cross for the capture of the Somme Bridge in France.