Complex sentence: The fleeing Federals became bottled up on a bridge just north of the crossroads, with Confederate artillery raking them as they struggled to cross the narrow structure, upon which the retreat became a rout, and Forrest won one of the greatest victories in his career.
Split into simpler sentences: The fleeing Federals became bottled up on a bridge just north of the crossroads, with Confederate artillery raking them as they struggled to cross the narrow structure. This turned the retreat into a rout, and Forrest won one of the greatest victories in his career.