In the 16th, 17th and 18th centuries, the regenten were the rulers of the Dutch Republic, the leaders of the Dutch cities or the heads of organisations. Though not formally a hereditary "class", they were de facto "patricians", comparable to that ancient Roman class. Since the late Middle Ages Dutch cities had been run by the richer merchant families, who gradually formed a closed group. At first the lower-class citizens in the guilds and schutterijen could unite to form a certain counterbalance to the regenten, but in the course of the 15th century the administration of the cities and towns became oligarchical in character. From the latter part of the 17th century the regent families were able to reserve government offices to themselves via quasi-formal contractual arrangements. In practice they could only be dislodged by political upheavals, like the Orangist revolution of 1747 and the Patriot revolt of 1785.