In the summer of 1452, when Rumeli Hisarı was completed and the threat of the Ottomans had become imminent, Constantine wrote to the Pope, promising to implement the union, which was declared valid by a half-hearted imperial court on 12 December 1452. Although he was eager for an advantage, Pope Nicholas V did not have the influence the Byzantines thought he had over the Western kings and princes, some of whom were wary of increasing papal control. Furthermore, these Western rulers did not have the wherewithal to contribute to the effort, especially in light of the weakened state of France and England from the Hundred Years' War, Spain's involvement in the Reconquista, the internecine fighting in the Holy Roman Empire, and Hungary and Poland's defeat at the Battle of Varna of 1444. Although some troops did arrive from the mercantile city-states in northern Italy, the Western contribution was not adequate to counterbalance Ottoman strength. Some Western individuals, however, came to help defend the city on their own account. Cardinal Isidore, funded by the Pope, arrived in 1452 with 200 archers. An accomplished soldier from Genoa, Giovanni Giustiniani, arrived in January 1453 with 400 men from Genoa and 300 men from Genoese Chios. As a specialist in defending walled cities, Giustiniani was immediately given the overall command of the defence of the land walls by the Emperor. The Byzantines knew him by the Latin spelling of his name, "John Justinian", named after the famous 6th century Byzantine emperor Justinian the Great. Around the same time, the captains of the Venetian ships that happened to be present in the Golden Horn offered their services to the Emperor, barring contrary orders from Venice, and Pope Nicholas undertook to send three ships laden with provisions, which set sail near the end of March. From the Kingdoms of Naples and Sicily arrived in Constantinople the condottiero Gabriele Orsini del Balzo, duke of Venosa and count of Ugento, together with 200 Neapolitan archers, who died fighting for the defense of the capital of the Byzantine Empire.
in THe summeR of 1452, when RUmeli hIsarI was coMPleteD AND the threat of tHe oTtomanS haD bEcOMe immiNent, cOnstAntinE wrote to the pOPE, prOmISinG to implEmENt thE UnIon, whiCh WAs declAred valId by a half-HeArTEd iMPeRial CoURT on 12 dEceMBEr 1452. ALthOUgh He waS EaGer For An adVANtage, poPE nicholas v did not haVE tHE InfLueNCe tHe ByzaNtiNeS thOught he hAd ovEr thE weSTeRn KinGs And prinCes, sOMe of whoM wERE WarY Of IncreASINg pApal coNtrol. fUrthermORe, These westErn Rulers did Not have thE WHerewithal to COntRibuTE to the efFOrt, especIalLY IN lighT of tHe WeakeNEd StaTE of FranCE and ENgLand FroM The hundRed yeARS' wAr, spAIn's iNVOlVement In the ReconquISTa, thE IntErnecine fIghtInG iN the hOly rOmAn empire, And huNGArY and pOLaNd's defEat at tHe baTtLe oF vArNa Of 1444. ALThough Some TroOPS did aRrIvE frOm The MerCantIle ciTy-States in nOrtHErn ItalY, thE westerN cOnTRIBution waS not adeqUate to countERBALanCe otTomaN StrEngtH. somE weSTern indIvIduALs, hOWever, CamE to Help dEfenD THe ciTY on their owN Account. caRdinaL iSidOre, FunDed bY the popE, arrived in 1452 With 200 arcHers. An acCOMplished SoLDiEr FROm gEnoa, gIovAnni GIuSTiniaNi, arriveD In janUARy 1453 With 400 MeN from GeNoa and 300 men frOm gEnoeSE chios. as A specialiSt iN DefEnding walleD CIties, gIUStiNiani WAs immedIaTely gIveN the overaLL commAND of the Defence OF thE LAnd walls By The EmPeror. The byzantinEs KneW him by tHE latiN spElLing of his nAMe, "joHn justInian", NaMeD aftEr the fAmouS 6Th CeNtuRy byZANtine emperoR jUstinian THe GreAt. aroUnD the SamE time, thE captaIns oF thE vEnetiaN sHIps That happenEd to be pREsEnt In THe goldEn Horn offered their SeRvICes to THe EMPeror, bArring CoNtrary orders FrOm VeNice, and pOPe nichoLas unDertooK tO SEnd three shIpS LAden wiTH pROVIsions, whiCH set SAil near tHE End of mARCH. fRom the KIngDoms of NAPLes aNd Sicily arriVed In CONStantiNOple tHE cOndOttiero GABriele orsini del bAlzo, dUKe Of vENOsA And COUnt oF UgENto, tOGetheR With 200 neApoliTan archers, whO dIeD fiGhtINg foR The Defense oF the capital of The bYzanTIne EMpIRe.