the fourth battle was called "operation diadem". the plan was that u.s. ii corps on the left would attack up the coast. the french corps would attack across the garigliano. british xiii corps in the centre right of the front would attack along the liri valley. on the right polish ii corps (3rd and 5th divisions) would attack the abbey. it took two months to get the troops ready. movements of troops was done in the darkness.