He began his service in the artillery regiment of the 10th Guards Tank Division of the 3rd Army of the Group of Soviet Forces in Germany.

In 1996, Major Korniychuk's division successfully conducted a field outing with combat fire, taking first place in the Armed Forces.

He graduated with honors from the operational and tactical level of the National Defense Academy of Ukraine, was appointed Deputy Brigade Commander of the 26th Artillery Division.

In 2011 he graduated from the National University of Defense of Ukraine and received an operational and strategic level of training.

[5] On 28 July 2021, Ukrainian President Volodymyr Zelenskyy dismissed several high ranking Ukrainian military commanders, General Korniychuk was dismissed from his position as Chief of the General Staff of the Armed Forces of Ukraine at that time.