«طَلَعْتُ إِلَى دِمْيَاطَ عَامَ هِيَاطٍ وَمِيَاطٍ»
I came to Damietta in a year marked by commotion and disturbance.
Ṭalaʿtu here describes arriving or appearing in a place. Hiyāṭ / miyāṭ are sound-linked terms suggesting a scene of quarrelling and disorder. Their matching endings give the prose a rhymed cadence.
The narrator does not identify one particular historical battle. The phrase establishes an unsettled wider climate, against which the fellowship of his companions will stand out.