In a July 2016 interview he described improvements in the military capabilities of his troops: “Although we lost a lot of experienced guys from the old squad, we've grown in quantity and quality.

We used to run with bobby pistols and sawn-off shots; now we have opportunities to work with tactical tank groups, armored vehicles, artillery support.

Many new possibilities opened for us: we can operate independently on the frontlines, free of other subunits that constantly let us down in combat operations.”[6][11] In September 2017 he was promoted to the rank of major and given control of the Azov Regiment, becoming the youngest commander in the Armed Forces of Ukraine.

[12][3] Following the full-scale Russian invasion of Ukraine, Prokopenko recorded a video message on 7 March 2022 in which he called for closing the skies over Ukraine to help avert humanitarian collapse in Mariupol, since “the enemy is breaking the rules of the war by shelling the civilian people and destroying the infrastructure of the city; the enemy is subjecting Mariupol to another genocide.”[13][14] On 19 March 2022, President Volodymyr Zelenskyy awarded the title Hero of Ukraine to the commanders of two units that led the defense of Mariupol: Prokopenko and the commander of the 36th Separate Marine Brigade, Colonel Volodymyr Baranyuk.

Major Denis Prokopenko received the highest honor “for bravery, for effective tactics to repel enemy attacks, and for protection of the hero city of Mariupol.”[5][8] On 12 April 2022, Prokopenko appeared in a video message, to report on charges that Russian chemical weapons had been dropped onto Mariupol in a drone attack: “Yesterday the occupiers used a poisonous substance of unknown origin against military and civilians in Mariupol.

Currently it's impossible to find out what substance poisoned people, because we are under complete blockade, and the site of the attack is under fire by the Russians to hide evidence of their crime.” Regardless of the sudden international focus on the chemical attack, he went on to claim that thousands of civilians in the city had been killed and continued to be slaughtered by constant ongoing Russian airstrikes, naval bombardment, heavy flamethrower systems, artillery, and phosphorus munitions.

[15][non-primary source needed] On 13 April 2022, it was confirmed by the official Twitter account of the Azov regiment that Prokopenko was promoted to the rank of lieutenant colonel.

[17][18][19][20][21] On 16 May 2022, a social media post was released by Prokopenko stating: "In order to save lives, the entire Mariupol garrison is implementing the approved decision of the Supreme Military Command and hopes for the support of the Ukrainian people."

Since the Russian Duma was attempting to classify Azov as a terrorist organization, the question of whether Russia considered Prokopenko as a prisoner of war (POW) remained in doubt.

[31] On 23 August 2023, Azov's press service published a photo of "Redis" at the command post on the front line holding a flag on the occasion of a national holiday.