The U.S. II Corps , with 34th Infantry Division under Maj. Gen. Charles W. Ryder spearheading the attack and French colonial troops on its right flank , launched an assault across the flooded Rapido valley north of Cassino and into the mountains behind with the intention of then wheeling to the left and attacking Monte Cassino from high ground .
The U.S. II Corps attacked across the Rapido valley north of Cassino .