At the beginning of the war in the summer of 1914, the general mobilization of Zagreb 13th Corps (including 42nd Home Guard Division) in the 5th Army and the Dalmatian-Herzegovinian 16th Corps under the 6th Army, were sent to Serbia, while Istrian and Međimuje troops were sent to Galicia. On 23 May 1915, 16th Corps was transferred from Serbia to the newly opened Italian Front, where it remained until the end of the war. Intention of the General Staff was clear – Croats from Dalmatia had a motive to fight against Italy, since they were directly threatened by the Italian plans of taking the eastern Adriatic coast according to the Treaty of London. On 27 February 1918, Zagreb 13th Corps was transferred to the battlefield of the Isonzo where it remained until the end of the war. At the end of the war, 84th Home Guard Brigade held a defensive position at Monte Groggio, while 83rd Brigade was in reserve near Belluno. On 22 October 1918, 83rd Brigade refused to replace the 84th Brigade at the position which was a sign of mass disobedience that was happening in the Austro-Hungarian Army. After the retreat from the Monte Groggio on 30/31 October 1918, 84th brigade entered Puster Valley near Bruneck. It was transported together with the 83rd Brigade from Carinthia to Croatia.