 The milk cows were priority targets for Allied forces, as sinking one milk cow would effectively curtail the operations of several regular U-boats and force them to return home for supplies.Ultra intercepts provided information concerning sailing and routing, and this, coupled with improved Allied radar and air coverage in the North Atlantic, eliminated most of them during 1943 including 4 lost in the month of July alone.By the end of the war all ten had been sunk.