The Emden Revolution of 18 March 1595 marked the beginning of the status of Emden as a quasi-autonomous city-state.
In 1595, after Count Edzard II had increased the tax burden several times and passed new laws, disregarding their effect on the citizens of Emden, the citizens revolted. They removed the city council, which Edzard II had appointed from office and occupied the count's castle. Edzard II was forced to move his residence to Aurich. Under the terms of the Treaty of Delfzijl of 15 July 1595, Edzard had to renounce most of his rights in Emden.
In the late 16th century, Emden took in many Calvinist refugees from the Spanish Netherlands and developed into a major port city of European importance, mainly because the warring Dutch and Spanish forces blocked each other's ports. Emden developed into a major transshipment point for grain imports to Westphalia. At the same time, the integration of the Calvinist refugees marked East Frisian society economically and religiously.
After the 1609 truce between Spain and the rebellious Netherlands, the port blockades were lifted and many refugees returned home. This led to an economic depression in Emden.
At the same time, tensions arose between the East Frisian town of Emden and Count Edzard II. The real reason was the arbitrary taxation by the count. As so often in history, the tensions exploded in a veritable religious conflict. Edzard's mother Anna had abolished the primogeniture in 1558, and decreed that the government of the county should be run jointly by her three sons, Edzard, Christopher and John. The goal of this decree was probably to dam the influence of the House of Vasa on the county. This influence was founded on the marriage between her eldest son Edzard and Catherine Vasa, the eldest daughter of King Gustav I of Sweden. This led to a religious division in the county, as John, like his mother and the majority of the citizens of Emden, was a Calvinist whereas Edzard was Lutheran.