Polish–Ottoman War (1485–1503)  The Polish–Turkish War of 1485-1503 was a prolonged conflict, rather a series of conflicts, between the Kingdom of Poland and the Ottoman Empire. The conflict formally lasted eighteen years, but during this time hostilities were ceased on several occasions due to temporary treaties being signed between the warring parties. The climax of the conflict was the disastrous King Jan Olbracht’s raid on Moldavia (1497, see also Battle of the Cosmin Forest). In the war the Kingdom of Poland was supported by its fiefs, the Duchy of Mazovia and the State of the Teutonic Order, as well as the Grand Duchy of Lithuania. The Ottoman Empire on the other hand, was backed by the Crimean Khanate, Moldavia, and Wallachia. For most of the 15th century, the Principality of Moldavia was a vassal of Poland, but at the same time other states, notably the Kingdom of Hungary and the Ottoman Empire together with the Crimean Khanate, tried to subdue Moldavia. After the Fall of Constantinople (1453), the Turks directed their expansion northwards, towards the lower Danube and behind the mighty river, which also threatened Poland. In 1485, Ottomans captured Black Sea ports Akkerman and Kilia. This undermined Polish eastern trade. The king promised help, calling pospolite ruszenie and Crown army, together with mercenaries. In November 1485, Poles commanded by Jan Karnkowski entered Moldavia, defeating some Tatar forces. Jan Olbracht himself prepared an anti-Ottoman raid in 1487, but had to change these plans and sent his forces to fight Tatars, allied with the Ottomans. On September 8, 1487, the Battle of Kopystrzyn in Podolia took place, in which the Tatars were defeated. On March 23, 1489, a two-year truce was signed between Poland and Ottoman Sultan Bayezid II, and on January 25, 1491 the Battle of Zaslaw in Volhynia took place, in which Polish forces destroyed a Tatar raid. In 1494 King Olbracht began military preparations for a new raid, despite a three-year truce, signed on April 6 of that year. Moldovan ruler Stephen III promised to help the Poles as soon as they reached Black Sea ports. It took Poland three years to complete preparations. Their army was made of Polish Crown forces, aided by a number of foreign mercenaries, 400 Teutonic Knights under Grand Master Johann von Tieffen, and a 600 strong unit from Mazovia.