Henry IV of France's succession to the French throne in 1589 occasioned a new civil war in France, in which Philip soon intervened on the Catholic side, offering the Dutch a respite from Parma's relentless pressure. Under the two stadtholders, Maurice and William Louis, the Dutch army was in a short time thoroughly reformed from an ill-disciplined, ill-paid rabble of mercenary companies from all over Protestant Europe, to a well-disciplined, well-paid professional army, with many soldiers, skilled in the use of modern fire-arms, like arquebuses, and soon the more modern muskets. The use of these fire-arms required tactical innovations like the counter-march of files of musketeers to enable rapid volley fire by ranks; such complicated manoevres had to be instilled by constant drilling. These reforms were later emulated by other European armies in the 17th century.