Complex sentence: In 1996, workmen at a construction site in the town of Towton uncovered a mass grave, which archaeologists believed to contain the remains of men who were slain during or after the battle in 1461.
Split into simpler sentences: In 1996, workmen at a construction site in the town of Towton uncovered a mass grave. Archaeologists believed the bodies in this grave were slain during or after the battle in 1461.