As such, Kolossváry took part in the Battle of Galicia in the early stages of the First World War, subordinate to Rudolf von Brudermann, who led the Austria-Hungarian 3rd army. Following the disastrous Austria-Hungarian defeat in that battle, and specifically the loss of Lemberg to the Russians, Kolossváry was in September 1914 removed from command of the 11th Army Corps. He got no further appointment, going on an indefinite leave of absence on 1 February 1915, and having no further part in the war.