The strongest restraint on the number of sailing warships was the large crews required, so fleets were limited by the number of seaman that could be induced or compelled to serve. England had a greater population and employed impressment to make up crew numbers, so could generally maintain more fully crewed ships than the Dutch could. The English navy of the Commonwealth period was in better condition and was still improving. The Commonwealth had won the English Civil War in 1652 with a strong and effective navy that had supported and supplied Cromwell's army in the wars in Scotland and Ireland; blockaded the Royalist fleet of Prince Rupert in Lisbon; and organised a system of convoys to protect the commerce of the Commonwealth against the numerous privateers based in European ports.