Complex sentence: During Napoleon's 1815 return from exile, the Old Guard was reformed, and fought at the Battle of Waterloo, where the "2e Regiment de Grenadiers-à-Pied" was pivotal in the defense of the town of Plancenoit against the Prussians.
Split into simpler sentences: During Napoleon's 1815 return from exile, the Old Guard was reformed, and fought at the Battle of Waterloo. The "2e Regiment de Grenadiers-à-Pied" was pivotal in the defense of the town of Plancenoit against the Prussians.