▁in ▁ 1 6 3 9 , ▁the ▁Duch y ▁of ▁Sax e - Al ten burg ▁passed ▁to ▁her ▁uncle ▁Duke ▁Frederick ▁William ▁II ▁and ▁her ▁cousin ▁Frederick ▁William ▁III . ▁ ▁The ▁Duch y ▁of ▁Sax e - G oth a - Al ten burg ▁was ▁nomin ally ▁created ▁in ▁ 1 6 7 2 , ▁when ▁Duke ▁Frederick ▁William ▁III ▁of ▁Sax e - Al ten burg ▁died ▁at ▁the ▁age ▁of ▁ 1 4 ▁and ▁Ernest ▁the ▁P ious , ▁by ▁his ▁marriage ▁with ▁Elisabeth ▁Soph ie , ▁inherited ▁the ▁major ▁part ▁of ▁his ▁poss essions . ▁It ▁was ▁common ▁for ▁the ▁Ernest ine ▁duch ies ▁to ▁merge ▁and ▁split ; ▁Ernest ' s ▁combined ▁du chy ▁was ▁divided ▁again ▁after ▁his ▁death ▁in ▁ 1 6 7 5 , ▁and ▁the ▁Duch y ▁of ▁Sax e - G oth a - Al ten burg ▁proper ▁came ▁into ▁existence ▁in ▁ 1 6 8 0 ▁with ▁the ▁completion ▁of ▁this ▁division ▁and ▁the ▁acc ession ▁of ▁his ▁el dest ▁son , ▁Frederick ▁to ▁the ▁sub div ision ▁centered ▁on ▁the ▁towns ▁of ▁Goth a ▁and ▁Al ten burg . ▁ ▁Frederick ▁had ▁already ▁served ▁as ▁reg ent ▁in ▁Sax e - Al ten burg ▁since ▁ 1 6 7 2 ▁and ▁assumed ▁responsibility ▁for ▁government ▁affairs ▁from ▁his ▁dise ased ▁father ▁two ▁years ▁later . ▁His ▁residence ▁remained ▁at ▁Fried en stein ▁Castle ▁in ▁Goth a , ▁he ▁also ▁had ▁the ▁Bar o que ▁palace ▁of ▁Friedrich swer th