In March, 1453, the armed forces of Mehmed II, numbering 160,000, completely surrounded Constantinople. The Greeks had only 5000 soldiers and 2000 Western knights, commanded by Giustiniani of Genoa. Notwithstanding this serious disadvantage, the city held out against the enemy for two months.
But on the night of 28 May, 1453, Mehmed II ordered a general assault. After a desperate conflict, in which Emperor Constantine XII perished, the Turks entered the city from all sides and perpetrated a frightful slaughter. Mehmed II rode over heaps of corpses to the church of St. Sophia, entered it on horseback, and turned it into a mosque.
When Constantinople fell to the Turks under Sultan Mehmed II in 1453, it was indeed a great shock to Christendom, and it brought the “Turkish peril” to the forefront of public opinion.
The recovery of Constantinople rather than of Jerusalem now became the crusading ideal of the Europeans that “were moved to contemplate war against the infidel”.
At least it meant that the object of new crusades had to deal with the Turks first before one could consider the re-conquest of Jerusalem, as this objective did not disappear from crusade treatises or crusade plans of the fifteenth and sixteenth centuries.
It might still be mentioned in papal bulls and letters; and in letters of indulgence the indulgence formula continued to include the words “ad recuperationem Terre Sancte”.
News of the fall of Constantinople reached Germany in the summer of 1453.
Aeneas Sylvio Piccolomini wrote to Pope Nicholas V on 12 July 1453 from Graz, where he had been with the Emperor’s court since May, on the “horrible news … of the loss of Constantinople – if only it were false”.
Aeneas wrote:“Your holiness has done what he could. There is nothing for which you can be blamed, but posterity without knowledge of the facts will attach this disaster to your name when it has learned that Constantinople was lost in your time … Now we see one of the two lights of Christendom extinguished … Now Mehmed reigns among us. Now the Turk hangs over our very heads. The Black Sea is closed to us, the Don has become inaccessible. Now the Vlachs must obey the Turk. Next his sword will reach the Hungarians, and then the Germans. In the meantime we are beset with internecine strife and hatred. The kings of France and England are at war; the German princes fight amongst themselves. Rarely is all Spain quiet; our own Italy is without peace … How much better we might turn this abundance of arms and unceasing warfare against the enemies of the faith. I know not, most blessed father, to whom more than your Holiness this responsibility belongs. You must rise up; write to the kings; send legates; warn, exhort the princes and the communities to assemble in some place of meeting or to send further their envoys. Right now while the evil is fresh in mind, let them hasten to take council for the Christian commonwealth. Let them make a peace or truce with their fellow Christians, and with joined forces take up arms against the enemies of salvation’s cross”.
All his life Aeneas had been engaged in the efforts to organize crusades against the Turks. As early as at the Council of Basel in 1436, he had delivered an oration in which he lamented the power of the Turks.
Nicholas V issued a crusading bull on 30 September 1453 summoning the Christian nations to a crusade for the recovery of Constantinople, and stigmatized Mehmed II. as the dragon described in the Book of Revelation.Absolution was offered to those who would spend six months in the holy enterprise or maintain a representative for that length of time. Christendom was called upon to contribute a tenth. The cardinals were enjoined to do the same, and all the papal revenues accruing from larger and smallerbenefices, from bishoprics, archbishoprics and convents, were promised for the undertaking.
In order for the crusade to succeed, the pope ordered (perspicimus) that “all kings and princes and all who hold dominion among the Christian people, to keep and observe the peace, on the authority of the omnipotent God”. He ordered that peace should be kept all over the Christian world, and that ecclesiastical authorities should excommunicate those who did not uphold the peace.
Emperor Frederick III [the patron of Pius II] called for several crusading assemblies to meet in 1454 and 1455 to discuss the crusade, and in Burgundy, Portugal, and Aragon kings and dukes were involved in the many great plans. The first Reichstag to discuss the crusade was to be held in Regensburg in the spring of 1454.Duke Philip of Burgundy appeared with great ceremony, but the emperor himself stayed away.
The Emperor had also invited a number of other princes of the Reich and of Europe as well as the major kings of Europe to be present at what has been termed the first crusade Reichstag.
Aeneas Sylvio Piccolomini gave an anti-Turkish oration at the Reichstag.
Aeneas was present at the next two councils that discussed the Crusade, in October in Frankfurt and in Wiener Neustadt in the spring of 1455.
The orations he delivered to the crusade Reichstags of 1454 and 1455 were famous. They described in detail the Turks’ atrocities at Constantinople, using Urban II’s famous speech at the council of Clermont in 1095 [whereby the First Crusade was initiated] as a model. Several were printed in his own time.
In 1456, he functioned as crusade preacher in Germany.
After the death of Nicholas V, Calixtus III became Pope. The crusade bull of Nicholas V was confirmed and reissued in May 1455 by Calixtus III with more regulations concerning the crusaders, the different forms of support, and the administration of indulgences. Calixtus III embarked on the construction of a fleet in the Tiber, even converting papal treasures into money to pay for it.
Calixtus opened his pontificate by vowing "to Almighty God and the Holy Trinity, by wars,, maledictions, interdicts, excommunications and in all other ways to punish the Turks." At a given hour daily the bells were rung in Rome that all mightgive themselves to prayer for the sacred war.
But to the indifference of most of the princes was added active resistance on the part of France. Venice, always looking out for her own interests,made a treaty with the Turks. Frederick III. was incompetent. The weak fleet the pope was able to muster sailed forth from Ostia under Cardinal Serampo to empty victories. The Hungarian,Hunyady, brought some hope by his brilliant feat in relieving Belgrade, on July 14, 1456, but the rejoicing was reduced by the news of the gallant leader’s death. Scanderbeg, the Albanian, who a year later was appointed papal captain-general, was indeed a brave hero, but, unsupported by Western Europe, he was next to powerless.
Despite his best efforts to promote a Crusade, Callixtus III died in August 1458 unsuccessful.
Aeneas was elected the successor of Callixtus III. The main plank in his "programme" was the raising of a Crusade against the Turks.
Crusade in the Fifteenth Century http://www.newadvent.org/cathen/04543c.htm#IX
Nicholas V http://www.newadvent.org/cathen/11058a.htm
Callixtus III http://www.newadvent.org/cathen/03187a.htm