Complex sentence: With his Eastern opponents still outside Chalcedon, in the spring of 622 Heraclius took the field, sailed his newly created army down the Ionian coast and landed at Issus, the exact site where Alexander the Great had decisively defeated the Persians some 1,000 years prior.
Split into simpler sentences: With his Eastern opponents still outside Chalcedon, in the spring of 622 Heraclius took the field. He sailed his newly created army down the Ionian coast and landed at Issus, the exact site where Alexander the Great had decisively defeated the Persians some 1,000 years prior.