With the outbreak of the First World War, Melnyk served as an officer in the Austro-Hungarian army as a volunteer commanding a company of the Ukrainian Sich Riflemen.

Due to his kind demeanor, he was referred to affectionately as "Lord Melnyk" by fellow Ukrainian and Austrian officers, who felt that he embodied the English concept of a gentleman, which at that time had been an ideal in Central Europe.

He retired from politics,[2] refrained from terrorist activities and worked as an engineer and as the director of forests on the huge estates of the Metropolitan of the Ukrainian Greek Catholic Church, Andrey Sheptytsky.

This information is part of the testimony that Abwehr Colonel Erwin Stolze gave on 25 December 1945 and submitted to the Nuremberg trials, with a request that it be admitted as evidence.

[6][7] After the June 1941 German invasion of the Soviet Union, Melnyk declared his own independent Ukrainian government in Rivne,[citation needed] competing with Bandera supporters for influence in western Ukraine.

In late 2006, the Lviv city administration announced the future transfer of the tombs of Andriy Melnyk, Yevhen Konovalets, Stepan Bandera and other key leaders of the OUN and UPA to a new area of Lychakivskiy Cemetery specifically dedicated to the Ukrainian national-liberation struggle.