▁Kal mar ▁Union ▁in ▁ 1 3 9 7 . ▁Sweden ▁broke ▁out ▁of ▁this ▁union ▁and ▁re - enter ed ▁it ▁several ▁times , ▁until ▁ 1 5 2 1 , ▁when ▁Sweden ▁finally ▁left ▁the ▁Union , ▁leaving ▁Den mark – N or way ▁( including ▁over se as ▁poss essions ▁in ▁the ▁North ▁Atlantic ▁and ▁the ▁island ▁of ▁Sa are ma a ▁in ▁modern ▁Est onia ). ▁ ▁Northern ▁Seven ▁Years ' ▁War ▁ ▁The ▁out break ▁of ▁the ▁Northern ▁Seven ▁Years ' ▁War ▁in ▁ 1 5 6 3 ▁is ▁mainly ▁attributed ▁to ▁Den mark ' s ▁dis ple asure ▁over ▁the ▁dis m ant ling ▁of ▁the ▁Kal mar ▁Union ▁in ▁the ▁ 1 5 2 0 s . ▁When ▁the ▁Dan ish - N or weg ian ▁king ▁Christian ▁III ▁( re igned ▁ 1 5 3 4 – 1 5 5 9 ) ▁included ▁the ▁tradition ally ▁Swedish ▁ins ign ia ▁of ▁three ▁crow ns ▁into ▁his ▁own ▁coat ▁of ▁arms , ▁the ▁Sw edes ▁interpreted ▁this ▁as ▁a ▁Dan ish ▁claim ▁over ▁Sweden . ▁In ▁response ▁Erik ▁XIV ▁of ▁Sweden ▁( re igned ▁ 1 5 6 0 – 1 5 6 8 ) ▁added ▁the ▁ins ign ia ▁of ▁Norway ▁and ▁Den mark ▁to ▁his ▁own ▁coat ▁of ▁arms . ▁ ▁After ▁Swedish ▁king ▁Erik ▁introduced ▁obst acles ▁in ▁an ▁attempt ▁to ▁h inder ▁trade ▁with ▁Russia , ▁Lü beck ▁and ▁the ▁Polish – L ith uan ian ▁Commonwealth ▁joined ▁Den mark – N