Complex sentence: To reach the Seine the division would have to cross three major rivers, and there were only two main lines of advance; one road running along the coast and another further inland from Troarn to Pont Audemer.
Split into simpler sentences: To reach the Seine the division would have to cross three main rivers, and there were only two main lines of advance. One road running along the coast and another further inland from Troarn to Pont Audemer.