In the next two battles, much smaller affairs on a narrow front around Cassino town, the corps was not involved. For the fourth and final battle the Fifth Army's front had been compressed towards the coast to allow the British Eighth Army's XIII Corps and II Polish Corps to join the line. During this battle, launched 11 May 1944, the Corps attacked into the inhospitable Aurunci Mountains which the Germans had considered impassable by modern infantry. The progress made by the corps and in particular the lightly loaded goumiers, capturing Monte Maio and pushing deep into the Aurunci, threatened the flanks of the German forces on their right in the Liri valley fighting against XIII Corps. The Germans were consequently forced to withdraw allowing XIII Corps to advance up the Liri valley and the Polish Corps on the right to occupy on 18 May the heights of Monte Cassino and the abbey reduced to rubble on top of it.