Complex sentence: In the following Battle of Picacho Pass the Barret's California cavalry engaged alone and suffered defeat in a brisk engagement, the Confederates watched the California cavalry retreat, then they fell back to Tucson, to warn Tucson's garrison of the approaching Union army.
Split into simpler sentences: In the following Battle of Picacho Pass the Barret's California cavalry engaged alone and suffered defeat in a brisk engagement. The Confederates watched the California cavalry retreat, then they fell back to Tucson, to warn Tucson's garrison of the approaching Union army.