He then defeated Sigtryg 's brother and successor Eystein , in a series of battles .
To secure his claim to Raumarike , Halfdan first defeated and killed the previous ruler , Sigtryg Eysteinsson , in battle .
Halfdan then defeated Sigtryg Eysteinsson 's brother and successor Eystein , in a series of battles .
To secure his claim to Raumarike , Halfdan first defeated and killed the previous ruler , Sigtryg Eysteinsson , in battle .