Murad II in the context of Janissary Corps

Gjergj Kastrioti (c. 1405 – 17 January 1468), commonly known as Skanderbeg, was an Albanian nobleman and military leader who led the League of Lezhë in the Ottoman-Albanian Wars until his death. Skanderbeg is considered to be a major figure of medieval Albanian history and today is the national hero of Albania.

A member of the noble Kastrioti family, Skanderbeg was sent as a hostage to the Ottoman court. He graduated from the Enderun School and entered the service of the Ottoman sultan Murad II (r. 1421–1451) for the next twenty years. His rise through the ranks culminated in his appointment as sanjakbey of the Sanjak of Dibra in 1440. During the Battle of Nish in 1443, he deserted the Ottomans and became the ruler of Krujë and nearby areas extending from Petrelë to Modrič. In March 1444, he established the League of Lezhë, with support from local noblemen, and unified the Albanian principalities.

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.

A ghazi (or gazi /ˈɡæzi/; Arabic: غازي ghāzī [ɣaːˈziː], pl. ghuzāt) is an individual who participated in ghazwa (غَزْو [ɣazw]), which are military expeditions or raids against Infidels. The latter term was applied in early Islamic literature to expeditions led by the Islamic prophet Muhammad, and later taken up by Turkic military leaders to describe their wars of conquest.

In the context of the wars between Russia and the Muslim peoples of the Caucasus, starting as early as the late 18th century's Sheikh Mansur's resistance to Russian expansion, the word usually appears in the form gazavat (газават).

The Treaty of Edirne and the Peace of Szeged were two halves of a peace treaty between Sultan Murad II of the Ottoman Empire and King Vladislaus of the Kingdom of Hungary. Despot Đurađ Branković of the Serbian Despotate was a party to the proceedings. The treaty brought an end to the Christian crusade against the Ottomans with significant gains. Within a month Vladislaus abjured his oath at the urging of the papacy and the crusade continued. On 10 November 1444 it ended in disaster at the Battle of Varna where the crusaders were wiped out and Vladislaus killed.

The treaty was started in Edirne with discussions between Murad and Vladislaus' ambassador. Within a few days, it was sent to Szeged with Murad's ambassador, to be finalized and ratified by Vladislaus. Once it arrived, complications caused the negotiations to continue for several more days, and oaths were eventually given in Várad. The ratification took place on 15 August 1444 in Várad.

A janissary (UK: /ˈdʒænɪsəri/ JAN-iss-ər-ee, US: /-sɛri/ -⁠err-ee; Ottoman Turkish: یڭیچری, romanized: yeñiçeri, IPA: [jeˈŋit͡ʃeɾ̞i], lit. 'new soldier') was a member of the elite infantry units that formed the Ottoman sultan's household troops. They were the first modern standing army, and perhaps the first infantry force in the world to be equipped with firearms, adopted during the reign of Murad II (r. 1421–1444, 1446–1451). The corps was established under either Orhan or Murad I, and dismantled by Mahmud II in 1826.

Janissaries began as an elite corps made up through the devşirme system of child levy enslavement, by which Christian boys, chiefly from the Balkans, were taken, levied, subjected to forced circumcision and forced conversion to Islam, and incorporated into the Ottoman army. They became famed for internal cohesion cemented by strict discipline and order. Unlike typical slaves, they were paid regular salaries. Forbidden to marry before the age of 40 or engage in trade, their complete loyalty to the Ottoman sultan was expected. By the 17th century, due to a dramatic increase in the size of the Ottoman standing army, the corps' initially strict recruitment policy was relaxed. Civilians bought their way into it in order to benefit from the improved socio-economic status it conferred upon them. Consequently, the corps gradually lost its military character, undergoing a process that has been described as "civilianization".

The siege of Thessalonica between 1422 and 1430 saw the Ottoman Empire, under Sultan Murad II, capture the city of Thessalonica. Afterwards, the city remained in Ottoman hands for the next five centuries until it became part of the Kingdom of Greece in 1912.

Thessalonica had already been under Ottoman control from 1387 to 1403 before returning to Byzantine rule in the aftermath of the Battle of Ankara. In 1422, after the Byzantines supported Mustafa Çelebi, a rival pretender against him, Murad, attacked Thessalonica. Unable to provide manpower or resources for the city's defence, its ruler, Andronikos Palaiologos, handed it over to the Republic of Venice in September 1423. The Venetians attempted to persuade the Sultan to recognise their possession, but failed as Murad considered the city his by right and the Venetians to be interlopers. This impasse led to an Ottoman blockade of Thessalonica, which occasionally flared up with direct attacks on the city. At the same time, the conflict was mostly fought as a series of raids by both sides against the other's territories in the Balkans and the Aegean Islands. The Venetians repeatedly tried to apply pressure by blocking the passage of the Dardanelles at Gallipoli, with little success.

Following the foundation of the Ottoman state, the title of Sheikh-ul-Islam (Turkish: Şeyhülislâm), formerly used in the Abbasid Caliphate, was given to a leader authorized to issue legal opinion or fatwa. His office was known as the Şeyhülislâm Kapısı, Bâb-ı Fetvâ, or Bâb-ı Meşîhat (The Sheikh's Porte). During the reign of Sultan Murad II, (1421–1444, 1446–1451) the position became an official title, with authority over other muftis in the Empire. In the late 16th century, the Shaykh al-Islam were assigned to appoint and dismiss supreme judges, high ranking college professors, and heads of Sufi orders. Prominent figures include Zenbilli Ali Cemali Efendi (1445–1526), Ibn-i Kemal (Kemalpaşazade) (1468–1533), Ebussuud Efendi (1491–1574) and al-Kawthari (1879–1952).

The Battle of Varna took place on 10 November 1444 near Varna in what is today eastern Bulgaria. The Ottoman army under Sultan Murad II (who did not actually rule the sultanate at the time) defeated the Crusaders commanded by King Władysław III of Poland and Hungary, John Hunyadi (acting as commander of the combined Christian forces) and Mircea II of Wallachia. It was the final battle of the unsuccessful Crusade of Varna, a last-ditch effort to prevent further Ottoman expansion into the Balkans.

The Muradiye Complex (Turkish: Muradiye Külliyesi) or the Complex of Sultan Murad II, the Ottoman sultan (reigned 1421–1451, with interruption 1444–46), is located in Bursa, Turkey. It is part of the historic UNESCO World Heritage Site.

The Green Tomb (Turkish: Yeşil Türbe) is a mausoleum of the fifth Ottoman Sultan, Mehmed I, in Bursa, Turkey. It was built by Mehmed's son and successor Murad II following the death of the sovereign in 1421. The architect Hacı Ivaz Pasha designed the tomb and the Yeşil Mosque opposite to it.

In addition to the sultan's sarcophagus, it contains seven other tombs: those of his sons Mustafa, Mahmud and Yusuf, his daughters Selçuk, Ayşe and Sitti and his wet nurse (Daye Hatun).

The Sword of Osman (Ottoman Turkish: تقلیدِ سیف; Turkish: Osman'ın Kılıcı) is an important sword of state that was used during the enthronement ceremony (Turkish: Kılıç alayı) of the sultans of the Ottoman Empire, from the accession of Murad II onwards. This particular type of enthronement ceremony was the Ottoman variant of the Bay'ah. The sword was named after Osman I, founder of the Ottoman dynasty.

Germiyan, or the Germiyanids (Old Anatolian Turkish: كرميان; Turkish: Germiyanoğulları Beyliği or Germiyan Beyliği), were a dynasty that controlled parts of western Anatolia from c. 1300 to 1429. Germiyan first appeared in the 12th-century chronicles of Matthew of Edessa and The Georgian Chronicles when they fought against the County of Edessa and the Kingdom of Georgia. They reappeared in historical records of 1239 near Malatya, where they were tasked with suppressing the Babai revolt. The tribe relocated to western Anatolia with the encroaching Mongol invasion. During the reign of Yakub I (r. 1300–40), Germiyan gained sovereignty with the demise of the Sultanate of Rum and forged war with the neighboring Ottomans and the Byzantine Empire, which continued during his successor Mehmed's rule (r. 1340–61).

Amidst political tension caused by the neighboring Karamanids, Suleiman (r. 1361–87) married his daughter Devletşah Hatun to the Ottoman prince and future sultan, Bayezid I (r. 1389–1402). The process saw a major dowry payment that transferred much of the Germiyanid realm to Ottoman control, including the capital Kütahya. Yakub II (r. 1387–90, 1402–11) was initially on friendly terms with the Ottomans but eventually attempted to reclaim the former lands that were lost following his sister's wedding. He was jailed by his brother-in-law Bayezid I in 1390, and Germiyan wholly came under Ottoman control. Nine years later, Yakub escaped from prison and sought the protection of Timur (r. 1370–1405), who, after defeating Bayezid with the help of Yakub at the Battle of Ankara in 1402, restored Germiyan's former boundaries. In 1411, Kütahya fell to Mehmed II of Karaman (r. 1398–99, 1402–20), interrupting Yakub's reign a second time. His rule was reinstated by the Ottoman sultan, Mehmed I (r. 1413–21), upon the defeat of the Karamanids. Although Yakub meddled with the internal conflicts within the Ottomans, the triumph of Murad II (r. 1421–44, 1446–51) over his opponents forced Yakub to revert to amicable relations. Yakub lacked male heirs and left the sultanate to Murad II in his will shortly before he died in 1429.

The siege of Svetigrad or Sfetigrad (Albanian: Rrethimi i Sfetigradit) began on 14 May 1448 when an Ottoman army, led by Sultan Murad II, besieged the fortress of Svetigrad (now Kodžadžik, North Macedonia). After the many failed Ottoman expeditions into Albania against the League of Lezhë, a confederation of Albanian Principalities created in 1444 and headed by Skanderbeg, Murad II decided to march an army into Skanderbeg's dominions in order to capture the key Albanian fortress of Svetigrad. The fortress lay on an important route between present-day North Macedonia and Albania, and thus its occupation would give the Ottomans easy access into Albania.

At the same time, Skanderbeg had been at war with Venice. Realizing the magnitude of his challenge, Skanderbeg attempted to relieve the garrison by engaging in skirmishes with the Ottoman army. His forces succeeded in inflicting heavy casualties on the Turkish forces through guerrilla-style attacks. Efforts were made by Skanderbeg to use intelligence forces, operating as far as Constantinople, to gather information on Murad's plans of action. Meanwhile, near Scutari, he had been able to defeat a Venetian force and managed to considerably weaken the Venetian presence in Albania. Despite these efforts, on 31 July the garrison of Svetigrad surrendered due to a disruption in the water supply. The garrison was spared and a force of Ottoman Janissaries was stationed inside the fortress instead. Two years later, Murad would march against Krujë, only to suffer a heavy defeat.