In 1917 – he was personal Adjutant General Secretary of Military Affairs Symon Petliura.

The following year – a member of the Ukrainian delegation at the peace negotiations in Brest.

14 December 1917, General Secretariat of the Ukrainian People's Republic issued mandate to Yuri Hasenko to perform special mission abroad.

He managed to carry out a number of important events of diplomatic and intelligence character in Vienna, Berlin, Paris, London, Rome, Washington and some other capitals.

[1] On 11 March 1920 – he was chairman of the Ukrainian national flying club in Vienna.