Giovanni Giustiniani Longo (Greek: Ιωάννης Λόγγος Ιουστινιάνης; Latin: Ioannes Iustinianus Longus) (died 1453) was a young Genoese captain, a member of one of the greatest families of the Republic, a kinsman to the powerful house of Doria in Genoa., and protostrator of the Eastern Roman (Byzantine) Empire. He led 700 professional soldiers, both Genovese and Greeks from the island of Chios, which at the time was part of the Republic of Genoa, to the defense of Constantinople against the Ottoman army of Sultan Mehmed II in 1453. (See also Fall of Constantinople.) He personally financed, organized and led this expedition on his own initiative, and upon arriving was placed in command of the land defenses by Emperor Constantine XI Palaiologos of the Byzantine Empire. Giustinani was key in contr