Already in 1587 Maurice was Stadholder of Holland and Zeeland.

In 1588 he became Captain-General and Admiral-General of the Union with the control and supervision of all the armed forces of the Provinces by sea and by land.

The death of Nieuwenaar in the following year created a vacancy in the stadholderates of Utrecht, Gelderland and Overyssel.

Maurice was in each province elected as Nieuwenaar's successor.

The Advocate therefore and the Prince, through the close accord which was for many years to subsist between them, gathered thus into their hands (except in Friesland) practically the entire administrative, executive and military powers of the United Provinces and by their harmonious co-operation with William Lewis, the wise and capable Stadholder of Friesland, were able to give something of real unity to a group of states, each claiming to be a sovereign entity, and to give them the outward semblance of a federal republic.