Giovanni Giustiniani Longo (Greek: Ιωάννης Λόγγος Ιουστινιάνης, romanized: Iōánnēs Lóngos Ioustiniánēs; Latin: Ioannes Iustinianus Longus; 1418 – 1 June 1453) was a Genoese nobleman, mercenary captain, and defender of Constantinople during its siege in 1453.

While it was originally a major power in the Eastern Mediterranean that outlasted many neighboring and competing empires, it had declined significantly in both influence and territory approaching the middle of the fifteenth century.

The loss that had the most influence on the state of Byzantium at the time of its fall was its temporary dissolution in 1204 when European crusaders conquered the city of Constantinople and drove the remaining Byzantine loyalists out of their seat of power.

Byzantium now only retained limited regional influence and had to contend with a younger and more militarily focused neighbor known as the Ottoman Empire looking to expand west into their territory.

Their ability to set up defenses against future attacks were also heavily hampered due to the fact that the empire was financially in a crisis and was unable to raise money through taxation because of Venetian resident's threats of evacuation if trade was further taxed which would have crippled its economy.

[4] The final factor that sets up the context of the state of Constantinople was the death of Ottoman Sultan Murad II, who had pursued a generally peaceful coexistence with Byzantium towards the end of his life.

When there was conflict within what would be constituted as modern-day Italy between city states, the employment of mercenaries was not only commonplace, but the preferred method of fielding soldiers.

[6] With that in mind, it is reasonable to assume that the Emperor sought a mercenary to lead the defense not only due to trust issues, but also a professional mercenary was more likely to understand military technology vital to properly organize the defense.Upon hearing of the plight of Constantinople, Giustiniani (along with 700 men from Chios and Genoa) sailed to defend the city, arriving in late January to prepare for the siege.

[7] Immediately, he reorganised the army, trained the city's recruits in modern weaponry, and removed men who had fled to monasteries with the hope of escaping military duties, instead directing them to Constantinople's defensive efforts.

[10] This tactic was impressive both due to its effectiveness given his limited resources, but also the fact this was his first time actively defending against the range and quantity of artillery the Ottomans were using.

[10] Giustiniani and his men were able to repel this attack after 4 hours due to the narrow front — as the breach had been a small one, the Ottoman troops were unable to take advantage of their superior numbers.

By late May, dwindling supplies and manpower coupled with the knowledge that no relief army would save Constantinople caused tensions to run high,[10] and amidst this Giustiniani and Notaras (the Byzantine chief minister) are reported to have had a falling out.

[12][13][14] Giustiniani's downfall came during this assault, when a cannon or crossbow bolt severely wounded his arm, chest or leg, forcing a retreat from his combat station.

These charges of cowardice and treason were so widespread that the Republic of Genoa had to deny them by sending diplomatic letters to the Chancelleries of England, France, the Duchy of Burgundy and others.

He was laid to rest at the Church of San Domenico in Pyrgi, Chios and although his tomb is lost (possibly from the 1881 earthquake), several descriptions survive.

Giustiniani appears in the text under the name Zuan Zustignan and is portrayed as a coward that fled his post and lied to the populace about the Ottomans breaking in to spread panic.

The first relevant secondary source to Giovanni Giustiniani's story came around in 2006 with William Caferro's John Hawkwood an English Mercenary in Fourteenth-Century Italy.

[5] While not being directly about him, it gives more information about how since mercenary work was scarcer in Italy there was a need for travel and what potential organizational structure he fit into before arriving at Constantinople.

But the part relevant to Giustiniani is how the record mentions that one of the reasons mercenaries had become such a relied upon force is that the Byzantine leadership lacked trust in native military leaders due to a mixture of incompetence and the threat of rebellion.

Though the streak of vocationally related publications would come to an end in 2011 with another direct reference to Giovanni Giustiniani and mark the beginning of more recent interpretations of his role in history.