Could the Seleucids have kept their eastern half? Is there any battle that could have gone differently and as a result the Seleucid Empire remains in its Eastern half? In the period of 100 years (200 BC-100 BC), the Seleucid Empire went from being about the size of Han Dynasty China to only controlling a small section of Levant. Could the parthian advance have been stopped, would it have been slower if the Seleucids hadn't insisted on fighting the Romans in Greece?