Count of Nassau-Dillenburg from 1606 to 1620, and stadtholder of Friesland, Groningen, and Drenthe. William Louis played a significant part in the Military Revolution of the 16th - 17th centuries. In a letter to his cousin Maurice of Nassau, Prince of Orange of December 8, 1594 he set out (from reading Aelianus Tacticus) an argument based on the use of ranks by soldiers of Imperial Rome as discussed in Aelian's Tactica. Aelian was discussing the use of the counter march in the context of the Roman sword gladius and spear pilium. William Louis in a 'crucial leap' realized that the same technique could work for men with firearms.
