In 1602 Enno III's troops laid siege to Emden, without success; On 8 April 1603 Enno had to sign the Treaty of The Hague in which he not only accepted the presence of a Dutch garrison in Emden, but agreed to pay the costs for the Dutch garrison.

In 1609 the conflict broke out again; the Emders were victorious in a skirmish at Greetsiel and temporarily occupied the Count's residence at Aurich.

On 24 May the Accord of Osterhusen was signed, which limited the sovereignty of the Count of East Frisia, stated the rights of the Estates (including Emden) and legitimised the Dutch garrison in Leerort.

Firstly, he married Countess Walburgis of Rietberg (1556–1586), daughter and heiress of Count John II of Rietberg, Lord of Esens, Stedesdorf and Wittmund and Countess Agnes of Bentheim-Steinfurt.

Three women, sisters Anna and Hille Evken, and their mother Stine Essken were burnt at the stake for this.