Thus one could characterise Poland-Lithuania in its final period ( mid-18th century ) , prior to the partitions as already not a completely sovereign state : it could be seen almost as a vassal , or in modern terms , a Russian satellite state , with Russian tsars effectively choosing Polish kings . Thus , one could characterise Poland-Lithuania in its final period ( mid-18th century ) , prior to the partitions as already not a completely sovereign state : it could be seen almost as a vassal state , or in modern terms , a Russian satellite state , with Russian tsars effectively choosing Polish kings .