A series of military conflicts between the Ottoman Empire and various European states took place from the Late Middle Ages up through the early 20th century. The earliest conflicts began during the Byzantine–Ottoman wars, waged in Anatolia in the late 13th century before entering Europe in the mid-14th century with the Bulgarian–Ottoman wars. The mid-15th century saw the Serbian–Ottoman wars and the Albanian-Ottoman wars. Much of this period was characterized by the Ottoman expansion into the Balkans. The Ottoman Empire made further inroads into Central Europe in the 15th and 16th centuries, culminating in the peak of Ottoman territorial claims in Europe.
The Ottoman–Venetian wars spanned four centuries, starting in 1423 and lasting until 1718. This period witnessed the fall of Negroponte in 1470, the siege of Malta in 1565, the fall of Famagusta (Cyprus) in 1571, the defeat of the Ottoman fleet at the Battle of Lepanto in 1571 (at that time the largest naval battle in history), the fall of Candia (Crete) in 1669, the Venetian reconquest of Morea (Peloponnese) in the 1680s and its loss again in 1715. The island of Venetian-ruled Corfu remained the only Greek island not conquered by the Ottomans.
In the late seventeenth century, European powers began to consolidate against the Ottomans and formed the Holy League, reversing a number of Ottoman land gains during the Great Turkish War of 1683–99. Nevertheless, Ottoman armies were able to hold their own against their European rivals until the second half of the eighteenth century.
In the nineteenth century the Ottomans were confronted with insurrection from their Serbian (1804–1817), Greek (1821–1832) and Romanian (1877–1878) subjects. This occurred in tandem with the Russo-Turkish wars, which further destabilized the empire. The final retreat of Ottoman rule began with the First Balkan War (1912–1913), and culminated in the signing of the Treaty of Sèvres after World War I, leading to the partitioning of the Ottoman Empire. The last of the Ottoman conflicts took place in 1923, where the empire reclaimed occupied lands in Anatolia from the Greeks, Armenians, French, and Italians. Istanbul, occupied by the combined Entente forces, was also recaptured.
Rise of the Ottomans (1299–1453)
Ottoman Emirate entered Europe amidst destructive civil war between John V Palaiologos and John VI Kantakouzenos and his son, Matthew Kantakouzenos. Ottomans were initially deployed as mercenaries allied with John VI and plundered Byzantine Thrace. They were granted the small fortress of Tzympe near Gallipoli. On 2 March 1354, the area was struck by an earthquake that destroyed hundreds of villages and towns in the area. Nearly every building in Gallipoli was destroyed, causing the Greek inhabitants to evacuate the city. Within a month, Süleyman Pasha seized the site, quickly fortifying it and populating it with Turkish families brought over from Anatolia.
Fall of Gallipoli in 1354 (or in 1356 – disputable due to a change in the Byzantine calendar), provided Ottomans with basis for operations in Europe, and thus started their westward expansion into the European continent. In 1361 Didymoteichon fell to the Turks. Orhan's successor, Murad I was more concerned with his Anatolian positions. However, Murad left the taking of Byzantine territory to his vassals with Philippopolis falling after major campaigning between 1363–64 and Adrianople succumbing to the Ottomans in 1369. Ottoman territory in Europe would thereafter known as Rumelia.
Ottoman advances into the Balkans were aided by further Byzantine civil conflict – this time between John V and his eldest son Andronikos IV. Thessalonica capitulated after four-year siege in 1387. Murad I fell on the plains of Kosovo and John V died a year later. Both were succeeded by Bayezid I and Manuel II respectively.
In 1394, Emperor Manuel II not only refused Bayezid I demands, he also refused to pay the Sultan tribute and went so far as to ignore the Sultan's messages, leading to a siege of the city in 1394. The siege was finally broken when Timur of the Timurid Empire led an army into Anatolia, dismantling the network of beyliks loyal to the Ottoman Sultan. At the Battle of Ankara, Timur's forces routed Ottoman forces and captured Bayezid I himself, a shocking defeat for which no one was prepared. In the aftermath, the Ottoman Turks began fighting each other led by Bayezid's sons. The Byzantines wasted no time exploiting the situation and signed a peace treaty with their Christian neighbours and with one of Bayezid's sons by which they were able to recover Thessalonika and much of the Peloponnese. The civil war would only end in 1413 when Mehmed I emerged as victor.
Murad II succeeded Mehmed while John VIII ascended to the Byzantine throne in 1421. This led to a deteriorated change in relations between the two as neither leader was content with the status quo. John VIII made the first and foolish move by inciting a rebellion in the Ottoman Empire: a certain Mustafa had been released by the Byzantines and claimed that he was Bayezid's lost son. Murad II's furious reply eventually smashed this upstart and, in 1422, began the Siege of Thessalonika that lasted for eight years before eventual Ottoman victory, and of the Constantinople itself. John VIII then turned to his aging father, Manuel II, for advice. The result was that he incited yet another rebellion in the Ottoman ranks — this time supporting Murad II brother's claim, Kucuk Mustafa. The seemingly promising rebellion had its origins in Asia Minor with Bursa coming under siege. After a failed assault on Constantinople, Murad II was forced to turn back his army and defeat Kucuk. With these defeats, the Byzantines were forced once more into vassalage – 300,000 coins of silver were to be delivered to the Sultan as tribute on an annual basis.
John VIII died in 1448 while Murad II died in 1451. Both were succeeded by Constantine XI and Mehmed II respectively. Constantine then proceeded to ask for a raise of Ottoman subsidy over Orhan Çelebi, grandson of Bayezid I and threaten his release to spark another civil war in the Ottoman Empire if refused. Mehmed used this as pretext to besiege Constantinople which fell on 29 May 1453, ending the Roman Empire.
The remaining Roman remnant states (Despotate of the Morea and Empire of Trebizond) fell in 1460 and 1461 respectively. Conquered European portion of Byzantine Empire, along with others was consolidated particularly into Beylerbeyli of Rumelia
In the latter half of the 14th century, the Ottoman Empire proceeded to advance north and west in the Balkans, completely subordinating Thrace and much of Macedonia after the Battle of Maritsa in 1371. Sofia fell in 1382, followed by the capital of the Second Bulgarian Empire Tarnovgrad in 1393, and the northwest remnants of the state after the Battle of Nicopolis in 1396.
A significant opponent of the Ottomans, the young Serbian Empire, was worn down by a series of campaigns, notably in the Battle of Kosovo in 1389, in which the leaders of both armies were killed, and which gained a central role in Serbian folklore as an epic battle and as the beginning of the end for medieval Serbia. Much of Serbia fell to the Ottomans by 1459, the Kingdom of Hungary made a partial reconquest in 1480, but it fell again by 1499. Territories of the Serbian Empire were divided between the Ottoman Empire, the Republic of Venice and the Kingdom of Hungary, with remaining territories being in some sort of a vassal status towards Hungary, until its own conquest.
Crusades against the Ottoman Empire
Pope Urban V initiated the Savoyard Crusade led by Count Amadeus VI of Savoy in 1366. Although intended as a collaboration with the Kingdom of Hungary and the Byzantine Empire against the growing Ottoman Empire in eastern Europe, the crusade was diverted from its main purpose to attack the Second Bulgarian Empire instead. There the crusaders made small gains that they handed over to the Byzantines. It did take back some territory from the Ottomans in the vicinity of Constantinople and on Gallipoli but all these conquests were reversed within less than five years by the Turks, when Andronikos IV returned it to the Turks for their support against his father, John V in the civil war.