in landing – 14 became bogged down in mud and only four were available for action. Operation Plunder, the Rhine crossing, began on the night of 23 March 1945. As well as the Staffordshire Yeomanry, DD tanks equipped the American 736th and 738th Tank Battalions and the British 44th Royal Tank Regiment. Some tanks were lost in the river, but the crossings were considered a success. The tanks were launched from points upstream from their objectives, to take account of the Rhine's strong current. Mats laid at the objective points (carried across beforehand by Buffalos) allowed the DDs to climb the steep, muddy banks of the river. The DD's last combat swimming operation was the Staffordshire Yeomanry's crossing of the River Elbe at Artlenburg on 29 April 1945. Italian campaign By February 1945, the 7th Queen's Own Hussars in Italy had been trained and equipped with DD tanks, both Shermans and Valentines. DD Shermans were successfully used in the crossing of the Po River on 24 April. On 28 April, those tanks still able to swim were used in an assault across the River Adige. During this operation, Valentine DDs were used to transport fuel (their only known use on active service). The tanks continued to be used in combat in the advance towards Venice. There were no further swimming operations, but it was found that the folded flotation screen offered a large seating area, making the tanks useful troop transports. "T-6 Device" An alternative to the DD was the "T-6 Device", developed by the US Army. Limited numbers of the "T-6 Device" were used by the US Army and Marines during the landings on Okinawa. The "T-6 Device" kit consisted of a structure of box-like, pressed-steel floats (pontoons) mounted on the front, rear and sides of a Sherman. No propellers were fitted – propulsion was provided by the rotation of the tracks. The front and rear floats were discarded on the beach, some in the water. Explosive bolts were used. Side floats were removed from the tanks on shore when the tactical situation permitted. In an oral interview with former Pvt. Maurice Dean Derby 37699146, Browning Automatic Rifleman, Co. A, 17th Infantry Regiment, 7th Infantry Division, he related that "On the night of the landing (Okinawa, 1 April 1945) we were kept awake all night because the Tank Crews were beating on the pontoons with sledgehammers to remove them