The szlachta, in its periodic opportunities to fill the throne, exhibits a preference for foreign candidates who will not found another strong dynasty.

This policy produces monarchs who are either totally ineffective or in constant debilitating conflict with the nobility.

Furthermore, aside from notable exceptions such as the able Transylvanian Stefan Batory (r. 1576-86), the kings of alien origin are inclined to subordinate the interests of the commonwealth to those of their own country and ruling house.

This tendency is most obvious in the prolonged military adventures waged by Sigismund III Vasa (r. 1587-1632) against Russia and his native Sweden.

On occasion, these campaigns bring Poland near to conquest of Muscovy and the Baltic coast, but they compound the military burden imposed by the ongoing rivalry with the Turks, and the Swedes and Russians will extract heavy repayment a few decades later.

The word hajduk, which had entered the Polish language from Hungarian in the late sixteenth century, was initially a colloquial term for a style of foot soldier, Hungarian or Turco-Balkan in inspiration, that has formed the backbone of the Polish infantry arm from the 1570s.

Unusually for this period, Polish-Lithuanian hajduks wear uniforms, typically of grey-blue woolen cloth, with red collar and cuffs.

Their principal weapon is a small caliber matchlock firearm, known as an arquebus.

For close combat they also carry a heavy variety of saber, capable of hacking off the heads of enemy pikes and polearms.

Contrary to popular opinion, the small axe they often wear tucked in their belt (not to be confused with the huge half-moon shaped berdysz axe, which is seldom carried by hajduks) is not a combat weapon but a tool for cutting wood.

Sultan Ahmed writes in 1614 to King Sigismund that he is sending Ahmed Pasha to punish “those bandits”, that this is not meant as a gesture of hostility to the Commonwealth, and that he asks of him not to be a host to fugitives; Ahmed Pasha writes hetman Żółkiewski asking for cooperation.

Żółkiewski answers that he has already done a lot in order to curb Cossack attacks, and that most of the Cossacks raiding Ottoman lands are not the Zaporozhian Cossacks of the Commonwealth, but rather Don Cossacks (and thus Muscovy subjects).

Żółkiewski's troops make another demonstration, but Ahmed Pasha does not attempt to cross the border, and settles for building new fortifications in the region of Ochakiv (Oczaków) in order to prevent future raids.

The Sultan, after yet another wave of Cossack raids in 1617, sends a powerful force under Iskander Pasha to the Commonwealth borders.

The army consists of janissaries, Tatars and vassal troops from Transylvania, Moldavia and Wallachia (numbering up to forty thousand).

Żółkiewski meets them near Busza (on the Jaruga River), but neither side can decide to attack, and letters between leaders have been exchanged since the start of Iskander’s march.

Żółkiewski has mostly magnate troops and no Cossack troops, as the Commonwealth is simultaneously waging war with Muscovy and with the latest Swedish aggression against Livonia, while the Ottomans are at war with Persia.

Żółkiewski is forced to renounce all Polish claims to Moldavia through the Treaty of Busza (also known as the "Treaty of Jaruga") signed with Iskander Pasha.

The treaty states that Poland will not meddle in the internal affairs of Ottoman vassals in Transylvania, Moldavia, and Wallachia, and that the Commonwealth is to prevent Cossacks from raiding lands in the Ottoman Empire, while ceding Khotyn.

The Turks promise in return to stop Tatar raids.

Osman vainly attacks Chocim (now in Moldova), on the Dniester, in 1612, where another Polish army of seventy-five thousand men, led by Stanislaus Lubomirski, fights the sultan’s army to a standstill.

The disgruntled Turkish troops, having suffered heavy losses, refuse to fight further.

A truce is signed soon after, but cross-border raiding continues.