Complex sentence: The southern column had to wait longer for an engagement, they moved slower than Colonel Loring's men partly because Bonneville split his force in two and marched it in tight configuration on both sides of the river.
Split into simpler sentences: The southern column had to wait longer for an engagement. They moved slower than Colonel Loring's men partly because Bonneville split his force in two and marched it in tight configuration on both sides of the river.