Complete the following sentence: 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. ️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️ 1609) and the Thirty Years' War (1618<unk>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. <unk> <unk> <unk> <unk> <unk> <unk>
Sack of Antwerp in 1576.