Battle of Dubno
When Nazi Germany attacked the Soviet Union in June 1941 Rokossovsky was serving as the commander of the 9th Mechanized Corps with the 35th and 20th Tank Divisions, and the 131st Motorized Division under his command.
He was immediately engaged in the early tank battles that raged around the Lutsk–Dubno–Brody triangle, also known as the Battle of Brody — an early Soviet counter-attack that was the most significant Soviet tank operation of the early stages of Operation Barbarossa.
The battle involved a large-scale attack involving five mechanized corps aimed at penetrating the German line in the direction of Lublin based on a plan developed before hostilities commenced. Orders for the attack from Zhukov were met with little enthusiasm from the Southwestern Front staff that wanted to maintain a defensive posture. Nonetheless, the attack proceeded. The operation met with numerous difficulties in mobilization, coordination, communication, transportation and execution but scored some initial successes, which were parried by the quick action of Von Rundstedt's Army Group South in Ukraine and ended in the destruction of most of the participating Soviet forces.
Upon receiving his orders Rokossovsky, whose divisions were stationed far to the rear of the frontier, had to commandeer trucks from the local reserve to carry munitions, and mount some of his infantry on tanks while the rest were forced to walk, splitting his forces. As a consequence, his forces were behind schedule and only an advanced guard were able to meet the 26 June "jump off", and entered the fray piecemeal. His orders were to move forward and take up positions around Lutsk north of the town of Dubno in co-ordination with the 19th Mechanized Corps under N. V. Feklenko, and attack south-west, while the Mechanized Corps of the 6th Army attacked northward from Brody to meet them, with the intent of cutting off the advance of the 11th Panzer Division east.
On 25 June, Rokossovsky's 131st Motorized were quickly driven out of their position at Lutsk by the 14th Panzer Division, but the 35th and 20th Tank divisions were able to cobble together advance forces to cut the Lutsk–Dubno road, even though their full force had not yet arrived on the battlefield. On the same day elements of the 19th Mechanized Corps, operating to his east out of Rovno, had succeeded in temporarily driving the rearguard of the 11th Panzer Division from Dubno, cutting off its advance units. In response the 13th Panzer Division attacked south from Lutsk the next day clearing Rokossovsky's forces from the road and allowing German infantry to recapture Dubno, while it drove off the 19th Mechanized and captured Rovno in Rokossovsky's rear. and refused a direct order, effectively ending the dispute between Zhukov and Kirponos: