Rubuta ci gaba don wannan sakin layi - Da yake fuskantar yakin da ke gabatowa da Sweden, gwamnatin Denmark ta so ta dauki Schack mai gogewa da daraja don babban mukami a rundunar sojojin Denmark. Don biyan bukatun Schack don matsayi na dindindin, an nada shi a shekara ta 1658 a matsayin Laftanar Janar, Kanar na doki da ƙafa, kuma ya zama memba na Majalisar Yaƙi. Ya kuma zama dan asalin Danish, yana karɓar gidaje biyu kyauta don rayuwa; Riberhus da Møgeltønder (daga baya Schackenborg Castle). A matsayin gwamnan soja, Schack ya umurci Copenhagen a lokacin da Sweden ta kewaye shi
na shekara ta 1659. Domin nasarar da ya samu na kare birnin, an ba shi lambar yabo tare da ci gaba zuwa filin-marshal. A cikin kaka na wannan shekarar, Schack ya jagoranci sojojin Denmark zuwa nasara a kan 'yan Sweden a yakin Nyborg.