During the Second World War stronger and heavier forest ploughs were developed and stronger tractors to pull these became available. The combination of more powerful crawler tractors en improved ploughs, made large-scale mechanical cultivation of upland moorland and heathland for forestry economically feasible by the end of the Second World War. By the early 1950s ploughing for drainage and cultivation was an established practice in the Forestry Commission and by 1970 the Commission ploughed at least 70 per cent of the annual planted area.