As Captain-General and Admiral of the Union, Maurice organized the Dutch rebellion against Spain into a coherent, successful revolt and won fame as a military strategist.

Under his leadership and in cooperation with the Land's Advocate of Holland Johan van Oldenbarnevelt, the Dutch States Army achieved many victories and drove the Spaniards out of the north and east of the Republic.

During the Twelve Years' Truce, a religious dispute broke out in the Republic, and a conflict erupted between Maurice and Van Oldenbarnevelt, which ended with the latter's decapitation.

The States of Holland and Zeeland paid for his studies, as their father had run into financial problems after spending his entire fortune in the early stages of the Dutch revolt.

He reorganized the Dutch States Army together with Willem Lodewijk, studied military history, strategy and tactics, mathematics and astronomy, and proved himself to be among the best strategists of his age.

Paying special attention to the siege theories of Simon Stevin, he took valuable key fortresses and towns during a period known as the Ten Glory Years: Breda in 1590, Zutphen, Knodsenburg in 1591, Steenwijk and Coevorden in 1592, Geertruidenberg in 1593, and Groningen in 1594.

His victories in the pitched battles at Turnhout (1597) and at Nieuwpoort (1600) were dependent on his innovation of cooperation between arms, with his cavalry playing a major role.

Previous generals had made use of drill and exercise in order to instill discipline or to keep the men physically fit, but for Maurice, they "were the fundamental postulates of tactics.

His reputation 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.

[8] Based on his 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.

These 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, or his disciples such as Gustavus Adolphus of Sweden, applied the Mauritian reforms to great effect in the remainder of the 17th century.

Against Maurice's advice, and despite his protests, Van Oldenbarnevelt decided to sign the Twelve Years' Truce with Spain, which lasted from 1609 to 1621.

With the religious troubles between Gomarists (strict Calvinists) and the Remonstrants (Arminians), the struggle between Van Oldenbarnevelt and Maurice reached a climax.

Important municipal regents such as Jacob Dircksz de Graeff and Cornelis Hooft from Amsterdam were temporarily removed from office by Moritz' powerful supporter Reynier Pauw.