By the summer of 1633, the relief force, led personally by the king and numbering about 25,000 (20,000 in the Polish–Lithuanian army, according to Jasienica), arrived near Smolensk; they reached Orsha on 17 August 1633. By the first days of September, the main body of the relief forces approaching Smolensk numbered around 14,000. The Russian army, recently reinforced, numbered 25,000. Only when Cossack reinforcements, led by Tymosz (Timofiy) Orendarenko and numbering between 10,000 and 20,000, arrived on 17 September would the Commonwealth army gain numerical superiority. The Cossacks under Orendarenko and Marcin Kazanowski raided the Russian rear lines, freeing the Polish–Lithuanian units under Radziwiłł and Gosiewski to join the effort to break the siege.