merchant port cities in the heart of the Ottoman Empire, which were just two days away by boat from the mouth of the Dnieper River. By 1615 and 1625, Cossacks had managed to raze townships on the outskirts of Constantinople, forcing the Ottoman Sultan Murad IV to flee his palace. His nephew, Sultan Mehmed IV, fared little better as the recipient of the legendary Reply of the Zaporozhian Cossacks, a ribald response to Mehmed's insistence that the Cossacks submit to his authority. Consecutive treaties between the Ottoman Empire and the Polish–Lithuanian Commonwealth called for both parties to keep the Cossacks and Tatars in check, but enforcement was almost non-existent on both sides. In internal agreements, forced by the Poles, the Cossacks agreed to burn their boats and stop raiding. However, boats could be rebuilt quickly, and the Cossack lifestyle glorified raids and looting. During this time, the Habsburg monarchy sometimes covertly employed Cossack raiders to ease Ottoman pressure on their own borders. Many Cossacks and Tatars shared an animosity towards each other due to the damage done by raids from both sides. Cossack raids followed by Tatar retaliation, or Tatar raids followed by Cossack retaliation, were an almost regular occurrence. The ensuing chaos and string of conflicts often turned the entire south-eastern Polish–Lithuanian Commonwealth border into a low-intensity war zone and led to an escalation of Commonwealth–Ottoman warfare, from the Moldavian Magnate Wars to the Battle of Cecora (1620) and wars in 1633–34. Cossack numbers expanded, with Ukrainian peasants running from serfdom in the Polish–Lithuanian Commonwealth. Attempts by the szlachta to turn the Zaporozhian Cossacks into serfs eroded the Cossacks' once fairly strong loyalty towards the Commonwealth. Cossack ambitions to be recognised as equal to the szlachta were constantly rebuffed, and plans for transforming the Polish–Lithuanian Two-Nations Commonwealth into a Polish–Lithuanian–Ruthenian Commonwealth (with the Ukrainian Cossack people) made little progress, owing to the Cossacks' unpopularity. The Cossacks' strong historic allegiance to the Eastern Orthodox Church put them at odds with the Catholic-dominated Commonwealth. Tensions increased when Commonwealth policies turned from relative tolerance to the suppression of the Orthodox church, making the Cossacks strongly anti-Catholic, which at that time was synonymous with anti-Polish. The waning loyalty of the Cossacks and the szlachta's arrogance towards them resulted in several Cossack uprisings against the Polish–Lithuanian Commonwealth in the early 17th century. Finally, the King's adamant refusal to bow to the Cossacks' demand to