Complex sentence: The electoral dignity had connected with it the obligation of primogeniture; that is, only the eldest son could succeed as ruler; this excluded the division of the territory among several heirs and consequently prevented the disintegration of the country.
Split into simpler sentences: The electoral dignity had connected with it the obligation of primogeniture; that is, only the eldest son could succeed as ruler. This forbade the division of the territory among several heirs, preventing the disintegration of the country.