Complex sentence: In August, 1818, Tikhanof painted an oil portrait of Baranov and a watercolor of Katlian and his wife, that were the only likenesses ever made during their lifetimes of the two long time antagonists who had finally made peace.
Split into simpler sentences: In August, 1818, Tikhanof painted an oil portrait of Baranov and a watercolor of Katlian and his wife. These were the only likenesses ever made during their lifetimes of the two long time antagonists who had finally made peace.