[1][better source needed] Ganchev received part of his education in France and spoken fluent French.

[5]: 746–748 On 3 August 1915, Ganchev traveled to the military headquarters of the German Empire on behalf of Bulgarian prime minister Vasil Radoslavov to negotiate Bulgaria's entry into World War I.

[4]: 90 From 1917 and 1918, Ganchev was one of two Bulgarian delegates that attended the proceedings that resulted in the signing of the Armistice between Russia and the Central Powers and the later Treaty of Brest-Litovsk.

[8]: 131–132 Towards the end of World War I, Ganchev was the commander-in-chief of Bulgarian forces on the Macedonian front.

Ganchev was one of the signatories of the Treaty of Neuilly-sur-Seine on 27 November 1919 that formally ended Bulgaria's participation in World War I.