Simplify the following text for a Grade 7 native English-speaking person.
Original: Duke Adolf however , stuck in a fierce inheritance conflict with his father Arnold , soon came under pressure from the Burgundian duke Charles the Bold , who had him captured and imprisoned in 1471 .
Simplified: Duke Adolf was fighting with his father Arnold about the inheritance of the land . Arnold came under pressure from the Burgundian duke Charles the Bold , who put him in prison in 1471 .