The fourth and final battle at Monte Cassino involved much larger troop formations compared to previous battles. Two months had passed since the previous attacks, and the time had been used to organize and maneuver large formations into position. This was in part due to the much improved spring weather with supported such an operation, as well as the additional gains that had been fought so hard for during the previous winter assaults. By May 11th, The British XIII corps would advance in Cassino town itself, which left the mountains surrounding the abbey to the Polish II Corps.