The speech is taken from the 'Anabasis of Alexander' (Book VII Chapter X), written around 130 AD by the Roman/Greek historian Arrian. Arrian had access to eyewitness accounts which are now lost (principally Ptolemy and Nearchus), and modern historians generally agree that this speech was a real historical event, and that Arrian gives a good representation of its likely content. Ultimately, however, this speech was written by Arrian, and Alexander's exact words are not known.