From 1871 to 1874 he was enrolled at the prestigious His Imperial Majesty Nicholas General Staff Academy and the Naval Cadet Corps.

Upon graduation, he was sent to the artillery brigade of the Caucasian Grenadier Division of Grand Duke Mikhail Nikolayevich and promoted to lieutenant on 13 April 1875.

In March 1894, after being promoted to the rank of Major General, Subotić was sent to the Russian Far East where he succeeded Paul Simon Unterberger as the military administrator of the Primorskaya Oblast on 27 May 1897.

Colonel (later Major General) Dmitry Horvat who would succeed Iugovich in 1903, was present in the capacity as head of administration of the Ussuri railway system.

The highlight of the event was when Subotić unfurled the CER flag, a symbol of Russian and Chinese partnership and cooperation before 80 foreign delegates who had arrived specifically for the occasion.

[5] Later, Subotić was sent to the city of Dalian to replace commander Oskar Starck on 18 September 1898 to July 1899 as military governor of Transcaspian Oblast.

At that time, Dejan Subotić was engaged in defending the Russian eastern coast of unrest caused by the Boxer Rebellion and the pacification of Manchuria.

During this time the Russian Imperial Geographical Society petitioned Subotić to allow Bronislaw Pilsudski to participate in Waclaw Sieroszewski's expedition to the island of Hokkaido to study the language of the Ainu people and their folklore for four months.

[10] In October 1903, Subotić wrote to Army Minister Aleksey Kuropatkin that Russia should exploit Vladivostok, not the city of Dalian, as suggested by Sergei Witte.