The logistical arrangements for D-Day proceeded well, although the initial advance was much slower than anticipated, and casualties and ammunition expenditure were high. In the lead up to Operation Cobra, the breakout from Normandy, Com Z's Advance Section took over responsibility for the depots and installations in Normandy, except for the fuel dumps. During the subsequent pursuit across France and Belgium the advance was much faster than forecast. There was no time to establish intermediate supply dumps. Lee improvised with the road transport, the Red Ball Express, but logistic support of the armies depended on the repair of the railroad system, and the development of ports. The original plans to use ports in Brittany were abandoned in favor of Marseilles in the south, and Le Havre and Antwerp, which were captured by the British 21st Army Group.