Complex sentence: The colonel in turn passed this responsibility on to a corporal, who, unaware of the carefully planned time schedule, ignited the fuses at 1:00 in the afternoon, when the bridge was still crowded with French troops, and Oudinot's rearguard was still in Leipzig.
Split into simpler sentences: The colonel in turn passed this responsibility to a corporal, who was unaware of the carefully planned time schedule. The NCO ignited the fuses at 1:00 in the afternoon while the bridge was still crowded with retreating French troops and Oudinot's rearguard was still in Leipzig.