Military career
Maurice organized the Netherlands' rebellion against Spain into a coherent, successful revolt. Together with Willem Lodewijk, he reorganized the Dutch States Army. He studied military history, strategy and tactics, mathematics and astronomy; and proved himself to be among the best strategists of his age. The Eighty Years' War (1560s to 1648) challenged his style, and he proved himself a good leader by taking several Spanish outposts. Paying special attention to the siege-theories of Simon Stevin (1548-1620), he took valuable key fortresses and towns during a period known as the Ten Glory Years (1588 to 1598): Breda in 1590, Zutphen and Knodsenburg in 1591, Steenwijk and Coevorden in 1592, Geertruidenberg in 1593, and Groningen in 1594. In 1597 he went on a further offensive and took Rheinberg, Meurs, Groenlo, Bredevoort, Enschede, Ootmarsum, and Oldenzaal, and closed off the year with the capture of Lingen. These victories rounded out the borders of the Dutch Republic, solidifying the revolt and allowing a national state to develop behind secure borders. They also established Maurice as the foremost general of his time. Many of the great generals of the succeeding generation, including his brother Frederick Henry and many of the commanders in the English Civil War of 1642 to 1651 learned their trade under his command.
His victories in the pitched battles at Turnhout (1597) and at Nieuwpoort (1600) depended on his innovation of cooperation between arms, with his cavalry playing a major role. The victories earned him military fame and acknowledgement throughout Europe. Despite these successes, the House of Orange did not attain great respect among European royalty, as the Stadtholdership was not inheritable.
The training of his army was especially important to early-modern warfare and to the Military Revolution of 1560–1650. Previous generals had made use of drill and exercise in order to instill discipline or to keep their men physically fit, but for Maurice, they "were the fundamental postulates of tactics".
This change affected the entire conduct of warfare, since it required the officers to train men (in addition to leading them), decreased the size of the basic infantry unit for functional purposes (since more specific orders had to be given in battle, and the decrease in herd behavior required more initiative and intelligence from the average soldier). One major contribution was the introduction of volley fire, which enabled soldiers to compensate for the inaccuracy of their weapons by firing in a large group. It was first used in European combat at the battle of Nieuwpoort in 1600.
As part of his efforts to find allies against Spain, Maurice received Moroccan envoys such as Al-Hajari. They discussed the possibility of an alliance between Holland, the Ottoman Empire, Morocco and the Moriscos, against the common enemy: Spain. Al-Hajari's journey chronicles, authored in 1637, mention in detail the discussion for a combined offensive against Spain.
Maurice gained a reputation in his time and among historians as the first general of his age. His fame rests not as much on his ability to win and exploit field battles as it does on his expertise as a siege commander, military organizer, and innovator. Of his two great adversaries, Alexander Farnese, Duke of Parma, and Ambrogio Spinola, Maurice cautiously never allowed himself to be brought to battle with Parma and did not follow up chances to offer Spinola battle with forces in his favour on the Yssel in 1606. He was, however, dealt a defeat by the Spanish general at the battle of Mülheim in October 1605. Based on Maurice's preference for sieges and small-scale actions, historian David Trim states that it is difficult to reach a verdict on his ability as a tactician. Jonathan Israel notes that on one of the rare occasions when he did have to fight a major battle in the open – the 1600 Battle of Nieuwpoort – it did end with a Dutch victory, but this outcome was highly risky, and Maurice took care to extricate his army and to avoid a second such battle.
Maurice founded a whole new school of military professional practice. This pointed the way to the professional armies of the future by reapplying Roman tactics and innovating in the fields of logistics, training, and economics (e.g. paying troops regularly and on time). Many graduates of service under Maurice, such as his nephew, the Marshal Turenne (1611-1675), or his disciples such as King Gustavus Adolphus of Sweden (1594-1632), applied the Mauritian reforms to great effect later in the 17th century.
