The primary question of the present study is whether the sources of medieval Hungary could add any new information to the general knowledge about the siege of Constantinople in 1453. The article presents reports about the siege of the Byzantine capital and besides draws attention to their sources and the possible borrowings from contemporary European chronicles. It can be stated that before the professional historiography starting in Hungary in the 18th century, the Hungarian sources concentrated mainly on the anti-Ottoman struggles of János Hunyadi, and the siege was just described in quite general. From the 18th century on the Jesuit historian, Nicolaus Schmitt and the Lutheran scholar, Ignaz Aurel Fessler brought changes. The Jesuit Schmitt wrote in Latin the first historical work on the Ottoman Empire in Hungary, while Fessler discussed the siege of Constantinople in detail in the summary of his great Hungarian history. Both used the then published full source database of their age, in which the Byzantine chronicles translated into Latin in the 18th century meant novelties.
Based on the above-mentioned sources, we examined whether it is possible that in 1453 there was still peace between Hungary and the Ottoman Empire and furthermore that two Hungarian embassies appeared during the siege in the Ottoman Empire, calling on the Sultan to abandon the siege.
Since two documents preserved in Haus-, Hof- und Staatsarchiv in Vienna from the time of Emperor Friedrich III prove that the German-Roman emperor also urged the Sultan not to attack the city of Cosntantinople, it is probable, that the Kingdom of Hungary likewise made a similar move.