From today's perspective, Khosrow II's victories against Byzantium was a disaster, because not only all his conquests were wiped out within a decade or so, but his costly campaigns had ultimately exhausted the Sasanian empire and paved the way for a relatively minor, but determined, army of Arab Bedouins to conquer Iran. However, from the perspective of the years 618-620, the conquest of Byzantium territories all the way to Egypt, in conjunction with a successful campaign against the Turks on the eastern frontiers, vouched for an unparalleled achievement that could even eclipse the victories of his illustrious forefathers, namely Shapur I and Shapur II. It therefore stands to reason that Khosrow II did embark on such a commemorative project, and I shall try to prove that the Taq-e Bostan cave-monument was precisely carved for this purpose. The project must have been accompanied by a propaganda slogan that defined the limits of his empire as stretching "from India to the Nile," for this is the main theme of the monument, and as a slogan, it was absorbed into Persian memory to eventually reemerge under the Mongol dynasties of Iran, as both Nasir-od-din-e Tusi and Rashidoddin Fazlollah make use of it in praise of the Il-Khanid empire.