A state "from sea to sea" and Ottoman pressure
The Tatars often organised raids into these lands, and their attacks grew in strength after 1475 when the Crimean Khanate fell under the rule of Sultan Mehmed II and the Ottoman Empire. In 1482 the Crimean khan laid waste to Kiev and its surrounding areas. The attacks continued without abate. In 1498 the Tatars together with the Turks devastated Podolia and Halych. The Turks also attacked the GDL's neighbor of Moldova, which was influenced by Ottoman policies since the second half of the 15th century.
In 1420 the King of Poland Jogaila wrote in a letter to the Holy Roman emperor that the Turks had invaded Oltenia (Lesser Wallachia) and had reached Balagros Castle in Moldova. This is why King Jogaila charged Grand Duke of Lithuania Vytautas with helping the Moldovan ruler Alexander the Great in the war against the Turks. The latter looked for allies a number of times in order to counter the Turkish army. However in 1484 Ottoman Sultan Bayezid II occupied a part of Moldovan territory with the port town of Kiliya near the Danube delta and the port town of Belgorod (Akerman) near the River Dniestr, while in 1486 Moldovan Voivode Stephen III was forced to become a vassal of the Ottomans. After the Turks occupied the Moldovan coast, a part of its former border with the GDL near the Dniestr became the "new" border between the GDL and the now Turkish-occupied province. The first direct political contact took place between the GDL and the Ottoman Empire. In 1489 Ottoman Sultan Bayezid II addressed King of Poland Casimir in order to agree on the countries' borders and approve a two-year peace agreement.
Negotiations with the Sultan
On September 21st, 1538 the army of Ottoman Sultan Suleiman I took a part of Moldovan territory located the Prut and Dniestr rivers together with Bender and joined it to the already occupied cities of Akkerman and Kiliya, entrenching themselves firmly in the territory "near the Black Sea" between the Dniestr and Dniepr which, as the ruling elite of the GDL thought, belonged to their country. Near the mouth of the Dniepr in Ochakovo, the Turks established a garrison. A part of Bessarabia called Budjak, or southern Bessarabia, ended up in the hands of the Ottomans, where the Turkish province of Akkerman was established, which had four main cities: Akkerman, Kiliya, Ochakovo and Bender. Fearing further expansion of the Turks and aiming for peace and security, Poland and the GDL began negotiations with the Ottoman sultan concerning the delineation of the border and peace. The GDL raised the question of returning the territory "near the Black Sea" between the Dniestr and Dniepr as well as Ochakovo. It was in 1540 that the question of the borders of these countries was raised for the first time in Istanbul. The same year, the king of Poland selected officials that met with the Turks to survey the "border inhabitants" and demarcate the borders in certain areas.
The search for the right borders: as borne witness to by "old virtuous" people and the ruins of mosques
In 1541 ruler Sigismund the Old write the sultan from Vilnius, asking him to send his negotiators so they could meet with his official and examine and determine Poland and the GDL's borders with the Ottoman provinces. In 1542 in a letter from Ottoman ruler Suleiman I to King Sigismund the Old, he wrote about the argument that arose concerning the borders at the border of the Akkerman province and stated that more lands should belong to the Ochakovo district of the Crimean khan. A request was made to send officials that could look over and correct the borders. In the same year, Sultan Suleiman I addressed the ruler of the GDL and Poland, offering to examine the countries' borders. The king appointed noble Bernatas Matejevskis (from Poland) and Kristupas Kmitičius, the eldery of Ovruch, who were to survey "old and virtuous people" in the surrounding districts where the border was so they could show it.
The officials were required to demand the "earlier" border between the countries, which had existed "earlier" up until the conquering by the Ottomans. In later letters the sultan stated that he would appoint people to go to the meeting with the king's envoys, who would examine the borders together and correct their signs so the Turkish peoples would not let their animals graze on lands of the GDL, but only on the holdings of the Turks. An agreement was made that on September 15th, 1542 officials from Poland and the GDL would meet with the Ottoman negotiators and in a "friendly manner" check and determine the borders. But the determining of the state borders did not go particularly well, and the negotiations did not give any results, as each country often strove to set borders that were as beneficial as possible for themselves. Thus in November 1542 the Ottoman officials asserted that the borders they had offered were correct, as they covered territories where there were many "ruins of religious buildings of Islam." They proved that those territories had to belong to the Ottomans. This was a tactic of the Turkish negotiators, because the Ottomans would build a mosque or bury an important figure right in the territories they occupied, which would then become a pilgrimage site. This was an argument that justified their claims to their conquests.
Unrest at the border
The countries' borders were agreed upon later, though they were often violated. For example, in 1543 and 1544 the Tatars readied to carry out raids deep in GDL territory on several occasions. Conflicts of the border inhabitants were mentioned in one letter dating from 1543 from Sultan Suleiman I to King Sigismund the Old – attacks near Ochakovo, which had to be decided upon by officials. There were important trade routes that went from the ports of the Black Sea coast, which merchants would transport many luxury goods and spices among other things on, with the local inhabitants (Cossacks) often carrying out robberies. For example, in 1545 the Cossacks, who had gathered together 800 men, attacked and robbed the caravans of merchants of the Ottoman sultan and the Perekop khan. Most like it is due to this that there were clashes near the Dniepr and in Tavan' between the Tatars of Khan Sahib Giray and GDL Cossacks. There were casualties. In 1546, it was stated in a report by Bar Starosta Bernard Pretvich that the Tatars had devastated lands of the GDL and Volhyn. The Turks, wanting to stabilise the border, settled 5,000 Moldovan colonists close to Bender in August 1547 and established a border.
The negotiations of Poland and the GDL with the Ottoman Empire lasted several years, taking place from 1548 to 1553. The negotiations often ended without any results. The instability of the borders was largely due to the fact that there were few colonized "borders" that limited the encroachment of inhabitants from neighbouring countries. The Tatars were nomads, and it was difficult for them to understand what a border was that marked territories where they were not supposed to cross. As the spread of Ottoman conquests in the 17th century shows, the Turks were not ready to limit their plans for expansion with these agreements.
T. Čelkis, Lietuvos Didžiosios Kunigaikštystės sienos „prie Juodosios jūros" XV–XV a. // Istorija, t. 83 (3), 2011, p. 3–13. History