Complex sentence: The steamship SS "Irish Oak" was built in 1919 as the SS "West Neris" for the United States Maritime Commission (USMC), first operated by the United States Shipping Board (USSB), then by "Mississippi Shipping Company".
Split into simpler sentences: The steamship SS "Irish Oak" was completed in 1919 as the SS "West Neris", commissioned by the United States Maritime Commission (USMC). It was operated by the United States Shipping Board (USSB), then sold to the "Mississippi Shipping Company".