Complex sentence: Many officers (often the gentlemen amateurs) of existing units merged into regiments of the New Model Army became surplus to establishment and were discharged; these "reformadoes" demonstrated several times in London as they sought compensation or relief.
Split into simpler sentences: Many officers (often the gentlemen amateurs) of existing units merged into regiments of the New Model Army became surplus to the organization and were discharged. Such "reformadoes" demonstrated several times in London as they sought compensation or relief.