Complex sentence: The flank (i.e. the Light and Grenadier) companies of the 13th had been stationed nearby, and launched a bayonet charge against the American artillery emplacements, but they were far outnumbered and were repulsed.
Split into simpler sentences: The flank (i.e. the Light and Grenadier) companies of the 13th had been stationed nearby. They launched a bayonet charge against the American artillery emplacements, but they were far outnumbered and were repulsed.