[1] On June 22, 1941, the first day of the German invasion, orders went out from headquarters Southwestern Front under Mikhail Kirponos to the mechanized corps to deploy forward as quickly as possible.
Meanwhile, south of Lutsk, the 11th Panzer Division secured Dubno, a vital road hub, against minimal resistance, and Kirponos ordered an immediate counter-attacked to retake it.
The German reaction was swift; the next day, June 26, the 13th Panzer Division struck down from Lutsk, catching the 9th Mechanized forward detachments in the flank, rolling them up and sending then reeling back, whilst German infantry opened up the 11th Panzer supply rout by recapturing Dubno.
The artillery Regiment of the 20th Tank Division deployed its newly issued 85mm Guns to cover the road and with direct fire repulsed the advancing Panzers".
The 25th Panzergrenadier Division reported extreme difficulty in holding back the attacks and suffered "serious losses" in the process.
[5] By the beginning of July, German armor had smashed a hole in the center of the Russian line, and the 13th Panzer stood at the edge of the Kiev fortified district.
[6] The 5th Army forces lunged southward and managed to cut the Zhitomir – Kiev highway, blocking III Panzer Corps' supply lines.
The corps now formed a component of 3rd Guards Tank Army, and fought under its command for the remainder of the war.