Complex sentence: He was defeated at Poley (Aguilar de la Frontera), and his son supported his kingdom with its capital in Bobastro, until Abderramán III forced them into exile in 928.
Split into simpler sentences: He was defeated at Poley (Aguilar de la Frontera). Samuel and his son ruled their land from Bobastro, until Abderramán III forced them into exile in 928.