The Commonwealth was relatively uninvolved in this war but the Polish King Sigismund III Vasa sent an elite and ruthless mercenary unit, the Lisowczycy, to aid his Habsburg allies in Vienna, since his brother-in-law was the Emperor.

In April 1621 an army of 120,000–160,000 soldiers[3][4] (sources vary), led by Osman II, advanced from Constantinople and Edirne towards the Polish frontier.

Approximately 25% of the Ottoman forces were composed of contingents from their vassal states: Tatars, Moldavians and Wallachians, a total of about 13,000 troops.

[5][dead link‍] In the meantime, the Commonwealth's Sejm, shaken by last year's defeat, agreed to raise taxes and fund a larger army, as well as to recruit large numbers of Cossacks.

The commander of Polish-Lithuanian forces, the Grand Lithuanian Hetman Jan Karol Chodkiewicz crossed the Dniester River in September 1621 with approximately 20,000 to 35,000 soldiers, joined by 10,000 more led by the future king of Poland, Prince Władysław Vasa.

In addition, two fortified camps were set in front of the main defence line: the Cossacks' and the mercenaries' (the famous Lisowczycy unit).

By 2 September, the main Ottoman army had arrived, and the siege began the day after the Cossacks joined the Polish camp.

Janissaries exploited the Poles' lack of vigilance, as they were sleeping, attacking on the right flank of the Commonwealth Army and storming into the Polish entrenchments, cutting down about a hundred infantrymen.

The Ottomans and Tatars were forced to retreat after suffering heavy losses, around 3,000 Janissaries died as a result of failed attack.

[10]: 370 After several costly and unsuccessful assaults in the first week of the siege, the Ottomans tried to take the fortress by cutting off their supply and reinforcements and waiting for them to succumb to hunger and disease.

On 24 September, a few days before the siege was to be lifted, the aged Grand Hetman died of exhaustion and illness in the camp.

[10]: 372 The lateness of the season, the loss of approximately 40,000 of his men in battle, the general exhaustion of the Ottoman army, the fact that his large force was also running out of supplies, and reportedly because of his illness compelled Osman II to accept a request from the defenders to start negotiations,[12][11]: 570  even though the Polish-Lithuanian forces were almost out of supplies (a legend has it that by the end of the siege, the Commonwealth army was down to its last barrel of gunpowder).

There were no territorial changes; the Commonwealth-Ottoman border was confirmed to be the Dniester River and the Commonwealth recognized Ottoman control over Moldavia.

Among the accounts of the battle is a rather one-sided one from Wacław Potocki's Transakcja wojny chocimskiej (The Progress of the War of Chocim),[8]: 347  written during the period 1669–1672.

It was based on the less-known Commentariorum Chotinensis belli libri tres ("Commentary on the Chocim War in three volumes") (diary, published in 1646) by Jakub Sobieski and other sources, now lost.

[15] However, the young Sultan was personally very unsatisfied with the result of the battle and the behavior of his household troops, the janissaries, during the campaign and started taking measures to reform the Ottoman military.

That attempt led to a revolt in Constantinople by the army, madrasa (religious school) students and wealthy merchants in May 1622, at the end of which Sultan Osman II was deposed and killed by the leaders of the mob.

In the peoples' coffee houses in Istanbul (up to the end of the 19th century) public storytellers used to relate the tales, many in poetry form, of the exploits of Young Osman (including Khotin) and his tragic demise.

[15] The Battle of Khotyn is commemorated on the Tomb of the Unknown Soldier, Warsaw, with the inscription "CHOCIM 2 IX - 9 X 1621/10 - 11 XI 1673".