Complex sentence: When a knyaz dies, his druzhina was inherited by his succesor, who usually already had his own druzhina, which was usually a source of rivalry: the duzhina of the previous kniaz claimed experience, while the newcomer one commanded the trust of the new leader.
Split into simpler sentences: When a knyaz died, his druzhina was inherited by his successor, who usually already had his own druzhina. This was usually a source of rivalry: the druzhina of the previous knyaz claimed experience, while the newcomers commanded the trust of the new leader.