"On the night of 10/11 April, British V Corps launched Operation Impact Plain to widen and deepen its bridgehead in the Wedge: 40th (Royal Marine) Commando advanced along the raised causeway bordering the lake while, from 56th (London) Division, 169th (Queen's) Brigade advanced on the commando's left across the flooded margins of the lake with two battalions in LVTs. The 56th Division's 167th Brigade advanced from the Wedge along the Reno flood banks.
The commando column met stiff resistance at the bridge north east of Menate and took heavy casualties but were able to take the objective with the assistance of air support. 42nd Jaeger Division seems to have been taken by surprise by their opponents' amphibious capacity and seemed somewhat unnerved by the LVTs emerging from the water so that by daylight on 12 April all three columns had made some 4 miles (6.4 km) headway, linking up in the Menate-Longastrino area. 169th Brigade then pushed forward on the road towards Filo and 167th Brigade continued up the Reno, rolling up the German defences as far as the confluence with the Santerno river to link with the Italian Cremona Combat Group which had advanced from the south.
Reacting to the Allied attack, von Vietinghof ordered 29th Panzergrenadier Division south to reinforce the Argenta gap. Its 15th Panzergrenadier Regiment arrived to reinforce 42nd Jaeger Division on 12 April but the rest of the division had been north of the Po and, delayed by air damage and fuel shortages was not in position until 14 April."