[1] Sargis Mehrabyan was one of the founding members of the Armenian Revolutionary Federation party and a close friend of leaders Kristapor Mikayelian and Simon Zavarian.

In the 1890s, he directed party activity in Iranian Azerbaijan, where he organized the transfer of people and supplies of weapons to fight against Ottoman Turkey.

At the time of the Hamidian massacres in the summer of 1896, he led the defense of villages in the region of the current Catak district in Western Armenia (now Turkey) and the Van province.

The following year, he was one of the leaders, along with Prince Hovsep Arghutian, who headed the Khanasor Expedition in Western Armenia, to fight against the ethnic cleansing carried out by the Kurdish Hamidiye irregulars commanded by Sharif Bey, who had a role in the Hamidian massacres with his cavalry.

In the summer of 1905, after the start of the Armenian–Tatar massacres, Vartan was called to his native Karabakh to organize and command the self-defense of the region against the exactions of the Azerbaijanis (Tatars).