Complex sentence: The allied army stormed the fortress of Anatha and moved on until it reached the region of Beth Aramaye in central Mesopotamia, near the Persian capital of Ctesiphon, but there they found the bridge over the Euphrates destroyed by the Persians.
Split into simpler sentences: The allied army stormed the fortress of Anatha and moved on until it reached the region of Beth Aramaye in central Mesopotamia, near the Persian capital of Ctesiphon. There, however, they found the bridge over the Euphrates destroyed by the Persians.