On 28 December 1943, the 69th Guards Tank Regiment expelled German forced from Koziatyn as part of the Zhitomir–Berdichev Offensive. Upon receiving orders to advance to Koziatyn, Boyko and his unit began a 35-kilometer march towards the city. The Germans fled in panic at the surprise advance, despite being numerically superior. The attack resulted in the destruction of 20 enemy tanks, one armored train, two vehicles, and two artillery batteries were destroyed. In addition, over a thousand German soldiers were killed and 150 captured. After the offensive, German forces launched a two-day counterattack. Boyko and his unit managed to hold the city despite heavy enemy fire while waiting for reinforcements. For his success in Koziatyn, he was awarded the title Hero of the Soviet Union on 10 January 1944. Less than a month later he was placed in command of the 64th Guards Tank Brigade, which would soon have success during the Proskurov-Chernivtsi operation. In March 1944 Boyko's brigade crossed the Dniester River, advanced 70 meters, and crossed the Prut river, and then advanced into the city of Chernivtsi. Because the brigade had advanced so quickly, they approached the city without many reinforcements and had to fight hard until the remainder of the 8th Guards Motorized Corps arrived before they could completely expel German forces from Chernivtsi. After the successful offensive in the city the 64th Brigade began to head towards Romania. On 26 April 1944 Boyko was awarded the title Hero of the Soviet Union a second time for his leadership of the brigade. He then went on to participate in the Lvov-Sandomierz and Berlin offensives.