In 1635/1636 the Estates and "Frederick II" agreed with Sweden upon the prince-archbishopric's neutrality. But this didn't last long, because in the Danish-Swedish Torstenson War (1643–45) the Swedes seized de facto rule in both prince-bishoprics. Christian IV of Denmark had to sign the Second Peace of Brömsebro on August 13, 1645, a number of Danish territories, including the two prince-bishoprics, were ceded into Swedish hands. So "Frederick II" had to resign as Administrator in both prince-bishoprics. He succeeded his late father on the Danish throne as Frederick III of Denmark in 1648.