Several other towns and fortresses in the region were the site of smaller battles. Russian forces captured several significant locations during their advance in 1632, but Nagielski speculates that the delay in the arrival of their main force and artillery at Smolensk caused by this dilution of effort may have cost them the siege and consequently the war. In July 1633, the Russians took the towns of Polatsk, Velizh, Usvyat, and Ozerishche. Polatsk was the scene of particularly heavy fighting as the Russians captured the city and part of the fortress. However, attacks on Vitebsk and Mstsislaw were successfully repulsed. Polish forces laid siege to Putivl, but due to the desertion of their Cossack allies they were forced to withdraw.