Péter Bara’s publication uncovers so far hidden details concerning the circumstances of the siege of Constantinople in 1453. The article presents the Latin text and a facing Hungarian translation of two unpublished letters which are kept today in the Haus-, Hof- und Staatsarchiv in Vienna. In the first letter Friedrich III the Holy Roman Emperor (r. 1452–1493) addresses the Sultan Mehmed II (r. 1444–1446, 1451–1481). The letter was sent from Wiener Neustadt 22 January 1453. Friedrich III confirms his awareness that the Sultan has built ramparts around the city and prepared other siege engines, as well. The emperor emphasises that Constantinople is a Christian city and since long time the capital of a Christian empire.
Friedrich warns the Sultan from further manoeuvres and counsels his colleague to withdraw from the city, otherwise allied Christian forces would march against the Ottoman troops.
The second letter was issued in Bavaria 29 January 1453 and guarantees safe conduct (salvus conductus) for two Franciscan friars. Franciscus Schesscerhsheriner of Nürnberg and Johannes of Bamberg were friars in the Constantinopolitan Fransciscan friary. In order to negotiate for the safety and well-being of the Constantinopolitan friary, Franciscus and Johannes together with some other compagnions visited some parts of the Roman Empire, presumably attending the imperial court. The letter meant to secure their return to Constantinople and release them from any tax, or levy in the course of their journey. The letter is a unique source, enlisting a number of late Medieval dignities and taxes.