Murad I in the context of "Ottoman Sultan"

Kırklareli Province (Turkish: Kırklareli ili) is a province in northwestern Turkey on the west coast of the Black Sea. The province neighbours Bulgaria to the north along a 180-kilometre (110 mi) long border. It borders the province of Edirne to the west and the province of Tekirdağ to the south and province of Istanbul to the southeast. Kırklareli is the capital city of the province. Its area is 6,459 km, and its population is 369,347 (2022). The province's and its central city's name means "the land of the forties" in Turkish and it may refer either to the forty Ottoman ghazis sent by the sultan Murad I to conquer the city for the Ottoman Empire in the 14th century or to the forty churches reported to be situated in the region before the Ottoman conquest, as attested by the former name of Kırklareli (Kırk Kilise in Turkish; Σαράντα Εκκλησιές). There is a memorial on a hilltop in Kırklareli city, called "Kırklar Anıtı" (the Memorial of the Forties in Turkish) to honor the Ottoman conquerors (For more on the name's origins, see Kırklareli). The province is bisected by the Yıldız (Istranca) mountain range. The north and northeastern parts of the province are among the least populated and under developed parts of Turkey. The districts to the south and west are more populated because the land is better suited for agriculture and industrial development. The north and eastern parts of the province are dominated by forests. Therefore, forestry is an important means of living in these areas. Fishing is done along the Black Sea coast.

The Battle of Kosovo took place on 15 June 1389 between an army led by the Serbian Prince Lazar Hrebeljanović and an invading army of the Ottoman Empire under the command of Sultan Murad I. It was one of the largest battles of the Late Middle Ages.

The battle was fought on the Kosovo field in the territory ruled by Serbian nobleman Vuk Branković, in what is today Kosovo, about 5 kilometers (3.1 mi) northwest of the modern city of Pristina. The army under Prince Lazar consisted mostly of his own troops, a contingent led by Branković, and a contingent sent from Bosnia by King Tvrtko I, commanded by Vlatko Vuković. Additionally, Lazar was also supported by a Christian coalition from various European ethnic groups. Prince Lazar was the ruler of Moravian Serbia and the most powerful among the Serbian regional lords of the time, while Branković ruled the District of Branković and other areas, recognizing Lazar as his overlord.

The sultans of the Ottoman Empire (Turkish: Osmanlı padişahları), who were all members of the Ottoman dynasty (House of Osman), ruled over the transcontinental empire from its perceived inception in 1299 to its dissolution in 1922. At its height, the Ottoman Empire spanned an area from Hungary in the north to Yemen in the south and from Algeria in the west to Iraq in the east. Administered at first from the city of Söğüt since before 1280 and then from the city of Bursa since 1323 or 1324, the empire's capital was moved to Adrianople (now known as Edirne in English) in 1363 following its conquest by Murad I and then to Constantinople (present-day Istanbul) in 1453 following its conquest by Mehmed II.

The Ottoman Empire's early years have been the subject of varying narratives, due to the difficulty of discerning fact from legend. The empire came into existence at the end of the 13th century, and its first ruler (and the namesake of the Empire) was Osman I. According to later, often unreliable Ottoman tradition, Osman was a descendant of the Kayı tribe of the Oghuz Turks. The eponymous Ottoman dynasty he founded endured for six centuries through the reigns of 36 sultans. The Ottoman Empire disappeared as a result of the defeat of the Central Powers, with whom it had allied itself during World War I. The partitioning of the Empire by the victorious Allies and the ensuing Turkish War of Independence led to the abolition of the sultanate in 1922 and the birth of the modern Republic of Turkey in 1922.

Lazar Hrebeljanović (Serbian Cyrillic: Лазар Хребељановић; c. 1329 – 15 June 1389) was a medieval Serbian ruler who created the largest and most powerful state on the territory of the disintegrated Serbian Empire. Lazar's state, referred to by historians as Moravian Serbia, comprised the basins of the Great Morava, West Morava, and South Morava rivers. Lazar ruled Moravian Serbia from 1371 until his death in 1389. He sought to resurrect the Serbian Empire and place himself at its helm, claiming to be the direct successor of the Nemanjić dynasty, which went extinct in 1371 after ruling over Serbia for two centuries. Lazar's programme had the full support of the Serbian Orthodox Church, but the Serbian nobility did not recognize him as their supreme ruler. He is often referred to as Tsar Lazar Hrebeljanović (Serbian: Цар Лазар Хребељановић / Car Lazar Hrebeljanović); however, he only held the title of prince (Serbian: кнез / knez).

Lazar was killed at the Battle of Kosovo in June 1389 while leading a Christian army assembled to confront the invading Ottoman Empire, led by Sultan Murad I. The battle ended without a clear victor, with both sides enduring heavy losses. In order to protect the weakened Serbian state from the Hungarian invasion from the north, Lazar's widow, Milica, who ruled as regent for their adolescent son Stefan Lazarević, Lazar's successor, accepted Ottoman suzerainty in the summer of 1390 in exchange for a military alliance.

Kosovo field (Albanian: Fusha e Kosovës; Serbian: Косово поље, romanized: Kosovo polje, lit. 'Blackbird Field') is a large karst field, located in the middle part of Kosovo. It is mostly known for being the site of the Battle of Kosovo (1389) between the Balkan Alliance led by Lazar of Serbia and Ottoman armies led by Murad I, and many other battles.

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".

Ziamet was a form of land tenure in the Ottoman Empire, consisting in grant of lands or revenues by the Ottoman Sultan to an individual in compensation for their services, especially military services. The ziamet system was introduced by Osman I, who granted land tenure to his troops. Later, this system was expanded by Murad I for his Sipahi.