Complex sentence: When she chased a Greek ship, she hoisted the Persian colours; but when she was chased by a Greek ship, she hoisted the Greek colours; so that the enemy might mistake her for a Greek, and give up the pursuit.
Split into simpler sentences: When she chased a Greek ship, she hoisted the Persian colours. But when she was chased by a Greek ship, she hoisted the Greek colours, so that the enemy might mistake her for a Greek and give up the pursuit.