Whakaotihia te rerenga e whai ake nei: I te tau 1810 ka noho a Boyen hei Kaiwhakahaere o te Kaabene o te Rōpū. I te whakahoutanga o te ope Prussian i mahi ia hei kaiawhina tino pukumahi a Scharnhorst, engari i muri i te mutunga o te hononga i waenga i Prussia me France i te tau 1812 i whakarere ia i tana komihana hei koroneela ka toro atu ki Vienna me St Petersburg. Ko nga huihuinga o te tau 1813 i kite ia i tana karanga ki te ratonga Prussian: hei koromatua i haere tahi ia me te ope a Ruhia mai i tana turanga i Kalisz ki Saxony. I muri i te
Te Pakanga o Lützen (2 Mei 1813) ko ia te kawenga mo nga kaitiaki rohe me te mutunga o te tiaki o Berlin. Engari i te wa o te rangimarie a Kingi Frederick William III i whakaingoatia ia hei Tumuaki o te Kaimahi Matua o te 3rd Army Corps. Na reira, i uru a Boyen ki nga pakanga me nga pakanga o te tau 1813 me te 1814 a ka eke ki te rangatira nui.