[1] Oleksandr was born to a peasant family of Udovidchenko from Cherkassy volost, Liven uyezd of Orel Governorate that moved Kharkiv.

With the break of the World War I Udovychenko was transferred to the 129th Bessarabia Regiment with which participated in military operations and was eventually wounded.

In January 1918 he was appointed a chief of staff for the Haidamaka Kosh of Sloboda Ukraine led by Symon Petlyura and participated in extinguishing of the Bolshevik Uprising at the Kiev Arsenal factory before the Ukrainian parliamentary elections.

During the times of the Ukrainian State he was appointed an assistant to the chief of intelligence of operation department headed by Vasyl Tyutyunyk (no relations to Yurii Tiutiunnyk).

On 31 October 1918 Udovychenko was appointed the head of the department in formation of a Special Army of Main Directorate of Ukrainian State General Staff.

Udovychenko managed to escape his captivity and in January 1920 with a group of military officers reached Mohyliv-Podilsky where he headed the formation of the 5th Ukrainian Brigade.

In emigration Udovychenko was promoted to Colonel General and was appointed the Minister of Defense of the Ukrainian National Rada Executive Committee.