Seine Commercial craft (barges and push-tows) can use the river from Marcilly-sur-Seine, to its mouth. At Paris, there are 37 bridges. The river is only above sea level from its mouth, making it slow flowing and thus easily navigable. The Seine Maritime, from the English Channel at Le Havre to Rouen, is the only portion of the Seine used by ocean-going craft. The tidal section of the Seine Maritime is followed by a canalized section ("Basse Seine") with four large multiple locks until the mouth of the Oise at Conflans-Sainte-Honorine (170 km). Smaller locks at Bougival and at Suresnes lift the
Seine River Crossing at Mantes-Gassicourt fulfilled a prophecy made a week earlier—that "the battle of Normandy is rapidly developing into the Battle of Western France." Having decided to send part of Patton's force down the west bank of the Seine, the Allied commanders saw a coincident opportunity to seize a bridgehead on the east bank of the river as a springboard for future operations. The XV Corps thus drew a double mission—the 5th Armored Division was to attack down the west bank while the 79th Infantry Division established a bridgehead on the east bank. In his order issued on 20 August, General Montgomery cautioned: "This