William Muir,
The Caliphate: Its Rise, Decline and Fall…
“ On Al-Medain being threatened, Yezdejird had despatched his family, with the regalia and treasure, to Holwan in the hilly country to the north: and now he contemplated flight himself in the same direction. The heart of Persia had sunk hopelessly; for otherwise the deep and rapid Tigris still formed ample defence against sudden assault. Indeed, the Arabs thought so themselves; for they were occupied many weeks in search of boats, which had all been removed from the western bank. Unexpectedly, a deserter apprised Sa'd of a place where the river could be swum or forded. ”
