The Army of Flanders ( ) was a multinational army in the service of the kings of Spain that was based in the Spanish Netherlands during the 16th to 18th centuries. It was notable for being the longest-serving standing army of the period, being in continuous service from 1567 until its disestablishment in 1706. In addition to taking part in numerous battles of the Dutch Revolt (1567–1609) and the Thirty Years' War (1618–1648), it also employed many developing military concepts more reminiscent of later military units, enjoying permanent, standing regiments ("tercios"), barracks, military hospitals and rest homes long before they were adopted in most of Europe. Sustained at huge cost and at significant distances from Spain, the Army of Flanders also became infamous for successive mutinies and its ill-disciplined activity off the battlefield, including the Sack of Antwerp in 1576.