Complex sentence: Led by CEO Thomas Usher, U.S. Steel spun off Marathon and other non-steel assets (except railroad company Transtar) in October, 2001, and expanded internationally for the first time by purchasing operations in Slovakia and Serbia.
Split into simpler sentences: Led by CEO Thomas Usher, U.S. Steel spun off Marathon and other non-steel assets (except railroad company Transtar) in October 2001. It expanded internationally for the first time by purchasing operations in Slovakia and Serbia.