Complex sentence: When James had succeeded to the English throne in 1603, England had acquired a new role in European affairs, as unlike the childless Elizabeth I, James by simply "having children, could play an important role in dynastic politics".
Split into simpler sentences: When James had succeeded to the English throne in 1603, England had acquired a new role in European affairs. Unlike the childless Elizabeth I, James by simply "having children, could play an important role in dynastic politics".