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Why did Denmark fight Sweden in the Northern Seven Years’ War?

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Denmark fought the Northern Seven Years’ War (1563–1570) primarily because King Frederick II aimed to reinstate the Kalmar Union and establish complete Danish hegemony in the Baltic Sea region.12

Following his accession to the throne in 1559, Frederick II sought to reassert control over Sweden, which had declared its independence from the union in 1523. By 1563, Frederick convinced the Rigsråd (the council of the realm) to agree to open warfare against Sweden to achieve these territorial and political goals.132

Ultimately, the conflict did not result in the restoration of the union. Denmark failed to gain a decisive military advantage, and the war concluded with the Peace of Stettin in 1570, leaving Sweden independent and Denmark burdened by significant debt.12