After Germany invaded the Soviet Union, Vlasenko, then a major, was released from the academy early in August 1941 and appointed commander of the 765th Rifle Regiment of the 107th Rifle Division. He led the regiment in the
Battle of Smolensk and the
Yelnya offensive. For its victory in the latter, the division was reorganized as the elite
5th Guards Rifle Division on 26 September, and Vlasenko's regiment became the 765th Guards Rifle Regiment. At the end of the month the division was assigned to the
49th Army, relocated to the region of
Kaluga, and by 9 October took up defenses along the east bank of the
Ugra river. Subsequently, the division took part in the
Vyazma and
Mozhaysk-
Maloyaroslavets defensive operations during the
Battle of Moscow. In December, Vlasenko took command of the 26th Separate Cadet Rifle Brigade and took part in the counteroffensive in the Battle of Moscow on the Maloyaroslavets axis. From January 1942 the brigade took part in combat operations on the
Kalinin Front, assigned to the
2nd Guards Rifle Corps. Vlasenko led the brigade in the
Toropets–Kholm offensive. In July Vlasenko, then a colonel, was placed at the disposal of the front Military Council and in August appointed deputy commander of the
243rd Rifle Division. Assigned to the
30th Army, the division took part in the
Rzhev–Sychyovka Offensive. From 22 September the division, as part of the
39th Army, took part in fighting to clear the northern bank of the
Volga. Reaching the Volga to the right of
Rzhev, the 243rd was withdrawn to the Western Front reserve on 1 October. The division was assigned to the 49th Army on 19 November and transferred to the
20th Army on 8 December, taking part in intense fighting to cut the Rzhev–Vyazma railway during
Operation Mars. Failing to accomplish the objective, the division went over to the defensive on 14 December. The 243rd was withdrawn to the
Reserve of the Supreme High Command on 29 December and on 22 January shifted to the
3rd Guards Army of the
Southwestern Front, taking part in the
Voroshilovgrad Offensive. During the Voroshilovgrad Offensive Vlasenko acted as commander of the division's 910th Rifle Regiment, and was awarded the
Order of the Red Banner for his performance. The recommendation read:During the battles for Voroshilovgrad from 6 to 14 February of this year, the 910th Rifle Regiment, under the command of Colonel Vlasenko, broke the sustained resistance of the enemy, taking ten settlements, wiping out a series of strongly fortified centers of enemy resistance, skillfully beating back a series of strong enemy counterattacks. In the battles for Voroshilovgrad the regiment took prisoners and trophies. For bold, decisive operations, fine organization of the battle, courage and valor, displayed in the battles with the German occupiers, he is recommended for a state award: the Order of the Red Banner.Vlasenko took command of the 3rd Guards Army's
259th Rifle Division on 19 March. The division defended a line along the
Seversky Donets in the regions of
Krasny Liman and
Slavyanoserbsk from 8 April. Vlasenko led the division in the advance through
Left-bank Ukraine between July and October, in which the 259th took part in the
Izyum–Barvenkovo offensive, the
Donbas strategic offensive, and the Zaprozhye Offensive. During these operations, the division liberated
Zolotoye,
Gorskoye, Nikitovka,
Artyomovsk, and
Popasnya. On 8 September the division received the Artyomovsk honorific in recognition of its performance in the liberation of that city. Vlasenko's division and its parent army were shifted to the
4th Ukrainian Front on 20 October and for the next three months took part in attacks against the German
Nikopol bridgehead. Promoted to major general on 17 November, he led the division in the
Nikopol–Krivoi Rog offensive and the assault crossing of the
Dnieper south of Nikopol between 3 February and 13 March 1944. After a short period of rest to receive replacements, the 259th resumed the attack in the
Odessa Offensive on 28 March. Crossing the
Southern Bug, the division developed the offensive to the southwest, and reached the
Dniester by 9 April, liberating up to 30 settlements. On the night of 13–14 April the division assault-crossed the Dniester in the region of
Oloneshty and Korkmaz, seizing a small bridgehead and fighting to hold it. As the offensive culminated, Vlasenko issued an illegal order to execute without trial 939th Rifle Regiment chief of artillery Major Fyodor Kiselyov for displaying cowardice on the battlefield. Kiselyov was publicly shot on 16 April in front of the division's officers. For this incident, Vlasenko was relieved of command on 22 May and placed at the disposal of the Military Council of the
3rd Ukrainian Front. Vlasenko was demoted to deputy commander of the
19th Rifle Division of the
57th Army on 21 July. He took part in the
Second Jassy–Kishinev offensive in this capacity, during which it fought in sustained battles on the
Prut and the destruction of encircled troops in the region of Minzhir and Chadyr. The division crossed the
Danube on 2 September, entering Romanian territory, and by 8 September reached the Bulgarian border. After taking part in the occupation of Bulgaria, the 19th fought in Yugoslavia and Hungary from 3 October, taking part in the
Belgrade offensive and the
Budapest offensive. During the Budapest offensive, Vlasenko took command of the 113th Rifle Division on 4 December. Blaming 157th Penal Company squad leader Captain Vladimir Nosovenko, mounted on horseback, for a delay in the movement of a column, Vlasenko shot and severely wounded him. Having only commanded the 113th for two days, for this incident, he was relieved of command on 6 December. Vlasenko was summoned to Moscow in January 1945 for the investigation of the case by Deputy People's Commissar of Defense
Nikolai Bulganin. The
Military Collegium of the Supreme Court of the Soviet Union, in a closed session, sentenced Vlasenko to five years of prison with the sentence deferred until the end of the war so that he could be sent back to the front. After conviction, Vlasenko was placed at the disposal of the Military Council of the
1st Ukrainian Front to await further assignment and in May was appointed deputy commander of the
88th Rifle Division of the
31st Army. == Postwar ==