Complex sentence: Anti-Confederate leader Albert Smith and Confederate Peter Mitchell were both Conservatives while one of the most prominent leaders of the pro-Confederation forces, Samuel Leonard Tilley, was a Liberal though he later joined the government of Sir John A. Macdonald.
Split into simpler sentences: Anti-Confederate leader Albert Smith and Confederate Peter Mitchell were both Conservatives, while one of the most prominent leaders of the pro-Confederation forces, Samuel Leonard Tilley, was a Liberal. Tilley later joined the government of Sir John A. Macdonald.