By 29 August, the Germans had largely withdrawn across the Seine River without their heavy equipment. The campaign through Northern France and Belgium was largely a pursuit, with the ports - formally designated "Fortress Towns" by the Germans - offering only limited opposition to the First Canadian Army. The advance was so rapid, 250 miles in four days, that Antwerp, Belgium, was captured undefended on 4 September 1944 and the port facilities were cleared of the German defenders in the following days.