Complex sentence: In late December, additional men from the 27th Alabama Infantry arrived along with 500 slaves to construct a small fortification across the river on Stewart's Hill, within artillery range of Fort Henry, and named it Fort Heiman.
Split into simpler sentences: In late December, additional men from the 27th Alabama Infantry arrived along with 500 slaves. They constructed a small fortification across the river on Stewart's Hill, within artillery range of Fort Henry, naming it Fort Heiman.