Upon the death of Edzard II in 1599, Enno assumed power and sought reconciliation with the East Frisian estates and the city of Emden. This led to the
Emden Concord later that year, which initially provided a constitutional basis for cooperation. He met and hosted Safavid ambassador
Hossein Ali Beg Bayat in same city later in 1601. Later however, Enno's chronic financial difficulties prompted him to impose a general tax across East Frisia. This provoked resistance, particularly in the city of
Norden and Emden, where citizens viewed it as overreach. Armed conflict ensued. Enno raised mercenary troops and built a redoubt at
Logum near Emden to cut off the city’s maritime access. In response, Emden appealed to the Dutch Republic, whose forces expelled Enno's troops in 1602 and established a permanent garrison in the city—a presence that lasted until 1744.On 8 April 1603 Enno had to sign the Treaty of
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. In 1611, Enno conceded further, allowing the Dutch to permanently occupy the fortress of
Leerort. This formalised East Frisia’s semi-vassal status to the Dutch and marked the effective loss of the county's autonomy in foreign and military affairs. In the
Accord of Osterhusen in 1611, Enno was forced to affirm the rights of the estates, codifying the dualism between princely authority and estate privileges in East Frisia. He ceded significant powers over taxation, military command, territorial governance, leasing rights, and clerical appointments. In 1615, recognising the Dutch dominance, Enno formally applied to incorporate East Frisia into the Dutch Republic, but the local estates rejected the proposal. Though East Frisia remained officially neutral during the Thirty Years’ War, its strategic location made it a target for exploitation. In 1621, at Dutch behest, the mercenary commander
Ernst von Mansfeld was quartered in the region. His troops committed widespread atrocities. Enno, virtually a prisoner in his castle at Esens, was powerless to resist. That same year, Mansfeld’s forces looted the 300,000 Reichstalers that had been prepared and sealed in barrels as compensation for Enno’s son-in-law, Prince
Gundakar of Liechtenstein. These debts remained a severe financial burden for the Cirksena family. In 1625, shortly after the departure of Mansfeld’s troops, East Frisia was struck by the devastating
storm tides of the North Sea, compounding the crisis. Enno died on 19 August 1625 in Leerort, his reign having begun with promise but ending in disaster and near-complete political collapse. ==Family and children==