John Hunyadi in the context of "Mehmed the Conqueror"

Mehmed II (Ottoman Turkish: محمد ثانى, romanized: Meḥemmed-i s̱ānī; Turkish: II. Mehmed, pronounced [icinˈdʒi ˈmehmet]; 30 March 1432 – 3 May 1481), commonly known as Mehmed the Conqueror (Ottoman Turkish: ابو الفتح, romanized: Ebū'l-fetḥ, lit. 'the Father of Conquest'; Turkish: Fâtih Sultan Mehmed), was twice the sultan of the Ottoman Empire from August 1444 to September 1446 and then later from February 1451 to May 1481.

In Mehmed II's first reign, he defeated the crusade led by John Hunyadi after the Hungarian incursions into his country broke the conditions of the truce per the Treaties of Edirne and Szeged. When Mehmed II ascended the throne again in 1451, he strengthened the Ottoman Navy and made preparations to attack Constantinople. At the age of 21, he conquered Constantinople and brought an end to the Byzantine Empire. After the conquest, Mehmed claimed the title caesar of Rome (Ottoman Turkish: قیصر روم, romanized: qayṣar-i rūm), based on the fact that Constantinople had been the seat and capital of the surviving Eastern Roman Empire since its consecration in 330 AD by Emperor Constantine I. The claim was soon recognized by the Patriarchate of Constantinople, albeit not by most European monarchs.

The Battle of Nish (early November 1443) was fought between the Crusaders led by John Hunyadi and Đurađ Branković and the Ottoman Empire led by Kasım Pasha. It saw the Crusaders capture the Ottoman stronghold of Nish (Niš) in Serbia, and defeat two armies of the Ottoman Empire. The Battle of Nish was part of Hunyadi's expedition known as the long campaign. Hunyadi, at the head of the vanguard, crossed the Balkans through the Gate of Trajan, captured Nish, defeated three Ottoman pashas, and after taking Sofia from the Ottomans, united with the royal army and defeated Sultan Murad II at Snaim (Kustinitza). The impatience of the king and the severity of the winter then compelled him (in February 1444) to return home.

In the Late Middle Ages, the Kingdom of Hungary, a country in Central Europe, experienced a period of interregnum in the early 14th century. Royal power was restored under Charles I (1308–1342), a scion of the Capetian House of Anjou. Gold and silver mines opened in his reign produced about one third of the world's total production up until the 1490s. The kingdom reached the peak of its power under Louis the Great (1342–1382) who led military campaigns against Lithuania, southern Italy and other faraway territories.

The expansion of the Ottoman Empire reached the kingdom under Sigismund of Luxembourg (1387–1437). In the next decades, a talented military commander, John Hunyadi, directed the fight against the Ottomans. His victory at Nándorfehérvár (present-day Belgrade, Serbia) in 1456 stabilized the southern frontiers for more than half a century. The first king of Hungary without dynastic ancestry was Matthias Corvinus (1458–1490), who led several successful military campaigns and also became the King of Bohemia and the Duke of Austria. With his patronage Hungary became the first country which adopted the Renaissance from Italy.

Kasım Pasha or Kasim Pasha (Turkish: Kasım Paşa; fl. 1442–43) was an Ottoman general and governor, the beylerbey of Rumelia and one of the commanders of the Ottoman forces during the Crusade of Varna (1443–44).

When Rumelian beylerbey and vizier Hadım Şehabeddin was defeated by John Hunyadi in 1442, he was replaced by Kasım Pasha at both positions.

The Crusade of Varna was an unsuccessful military campaign mounted by several European leaders to check the expansion of the Ottoman Empire into Central Europe, specifically the Balkans between 1443 and 1444. It was called by Pope Eugene IV on 1 January 1443 and led by King Władysław III of Poland, John Hunyadi, Voivode of Transylvania, and Duke Philip the Good of Burgundy.

The Crusade of Varna culminated in a decisive Ottoman victory over the crusader alliance at the Battle of Varna on 10 November 1444, during which Władysław disappeared and the expedition's papal legate Julian Cesarini was killed.

The siege of Belgrade, or siege of Nándorfehérvár (Hungarian: Nándorfehérvár ostroma or nándorfehérvári diadal, lit. "Triumph of Nándorfehérvár"; Serbian Cyrillic: Опсада Београда, romanized: Opsada Beograda) was a military blockade of Belgrade that occurred 4–22 July 1456 in the aftermath of the fall of Constantinople in 1453 marking the Ottomans' attempts to expand further into Europe. Led by Sultan Mehmed II, the Ottoman forces sought to capture the strategic city of Belgrade (Hungarian: Nándorfehérvár), which was then under Hungarian control and was crucial for maintaining control over the Danube River and the Balkans.

The Hungarian defenders, under the leadership of John Hunyadi, who had garrisoned and strengthened the fortress city at his own expense, put up a determined resistance against the larger Ottoman army. The siege lasted for several weeks, during which both sides suffered heavy losses. The defenders used innovative tactics, including the use of heavy artillery and firearms, to repel the Ottoman assaults. Hunyadi's relief force destroyed a Turkish flotilla on 14 July 1456 before repulsing their large scale assault to capture the city on 21 July. Wounded Mehmed II was compelled to lift the siege and retreat on 22 July 1456. This victory boosted the morale of European Christian forces and was seen as a turning point in their efforts as it provided a crucial buffer and temporarily halted Ottoman expansion in Europe.

Vlad III, commonly known as Vlad the Impaler (Romanian: Vlad Țepeș [ˈvlad ˈtsepeʃ]) or Vlad Dracula (/ˈdrækjʊlə, -jə-/; Romanian: Vlad Drăculea [ˈdrəkule̯a]; 1428/31 – 1476/77), was Voivode of Wallachia three times between 1448 and his death in 1476/77. He was regarded as a hero in Romania due to his opposition to the Ottoman Empire and he is considered an important ruler in Wallachian history.

He was the second son of Vlad Dracul, who became the ruler of Wallachia in 1436. Vlad and his younger brother, Radu, were held as hostages in the Ottoman Empire in 1442 to secure their father's loyalty. Vlad's eldest brother Mircea and their father were murdered after John Hunyadi, regent-governor of Hungary, invaded Wallachia in 1447. Hunyadi installed Vlad's second cousin, Vladislav II, as the new voivode. Hunyadi launched a military campaign against the Ottomans in the autumn of 1448, and Vladislav accompanied him. Vlad broke into Wallachia with Ottoman support in October, but Vladislav returned, and Vlad sought refuge in the Ottoman Empire before the end of the year. Vlad went to Moldavia in 1449 or 1450 and later to Hungary.

The House of Hunyadi was one of the most powerful noble families in the Kingdom of Hungary during the 15th century. A member of the family, Matthias Corvinus, was King of Hungary from 1458 until 1490, King of Bohemia (ruling in Moravia, Lower Lusatia, Upper Lusatia, and Silesia) from 1469 until 1490, and Duke of Austria from 1487 until 1490. His illegitimate son, John Corvinus, ruled the Duchy of Troppau from 1485 until 1501, and five further Silesian duchies, including Bytom, Głubczyce, Loslau, Racibórz, and Tost, from 1485 until 1490. The Hunyadi coat-of-arms depicted a raven with a golden ring in its beak.

The founder of the family, Voyk, received the eponymous Hunyad Castle (in present-day Hunedoara, Romania) from Sigismund, King of Hungary, in 1409. His ethnicity is the subject of scholarly debate. Some modern historians describe him as a Vlach, or Romanian, knez or boyar, from either Wallachia or Transylvania. Others describe him as a Cuman or Slav nobleman. According to the 15th-century historian, Johannes de Thurocz, Voyk moved from Wallachia to Transylvania. Voyk's oldest son, John Hunyadi, was often mentioned as a "Vlach" by his contemporaries.