In a series of fierce engagements, Commonwealth forces gradually overran the Russian field fortifications, and by 4 October the siege had broken.

Russia's aim was to gain control of Smolensk, which it had ceded to the Commonwealth in 1618 at the Truce of Deulino, ending the last Russo-Polish War.

The Russian army that crossed the Lithuanian border in early October 1632 had been carefully prepared and was under the experienced command of Mikhail Shein, who had previously defended Smolensk against the Poles during the 1609–1611 siege.

[7] Dissatisfied with their traditional formations of musket-equipped infantry (the streltsy), the Russians looked to foreign officers to update the equipment and training of their troops based on the Western European model of regulars, dragoons, and reiters.

[13] Despite these difficulties, the city, commanded by Deputy Voivode Samuel Drucki-Sokoliński,[14] held out throughout 1633 while the Commonwealth, under its newly-elected King Władysław IV, organised a relief force.

The Sejm officially sanctioned a declaration of war and authorised a large payment (6.5 million zlotys, the highest tax contribution during Władysław's entire reign) for the raising of a suitable force in Spring 1633.

By February 1633, they had amassed around 4,500 soldiers, including over 2,000 infantry, and were engaged in raiding the rear areas of the Russian besiegers to disrupt their logistics.

[14] Hetman Radziwiłł also managed to break through the Russian lines on several occasions, bringing about 1,000 soldiers and supplies into Smolensk to reinforce the fortress and raising the defenders' morale.

[3][11][12] By the summer of 1633, the relief force, led personally by the king and numbering about 25,000[3][5] (20,000 in the Polish-Lithuanian army, according to Jasienica), arrived near Smolensk; they reached Orsha on 17 August 1633.

[17] Only when Cossack reinforcements, led by Timofiy Orendarenko and numbering between 10,000 and 20,000, arrived on 17 September would the Commonwealth army gain numerical superiority.

[11][17][18] The Cossacks under Orendarenko and Marcin Kazanowski would raid the Russian rear lines, freeing the Polish-Lithuanian units under Radziwiłł and Gosiewski to join the effort to break the siege.

[6] In a series of fierce engagements, Commonwealth forces gradually overran the Russian field fortifications, and the siege reached its final stages by late September.