Within months of retirement, the First World War broke out. Kirchbach was reactivated and was assigned as the commanding general of the XII (Royal Saxon) Reserve Corps, part of the predominantly Saxon 3rd Army on the right wing of the forces that invaded France as part of the Schlieffen Plan offensive in August 1914. He served with this corps on the Western Front over the next three years. He fought in 1914 in the First Battle of the Marne, in 1915 in the First Battle of Champagne, in 1916 in the Battle of the Somme and at the Battle of Passchendaele at Ypres in 1917. For his service as a corps commander, he was decorated with the Pour le Mérite on 11 August 1916.