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
6th Airborne Division advance to the River Seine heavy anti-aircraft artillery regiment used in a field artillery role. In the operation the 6th Airborne Division together with the 7th Armoured Division, the 49th (West Riding) Infantry Division and the 51st (Highland) Infantry Division, formed the I Corps, attached to the First Canadian Army. When issuing his orders, Lieutenant General John Crocker, the Corps commander, aware that the 6th Airborne had almost no artillery, vehicles or engineer equipment, did not expect them to advance quickly. To reach the River Seine the division would have to cross three main rivers, along only two main lines of advance. One route was