He was one of the masterminds of the 1896 occupation of the Ottoman Bank in response to the Hamidian massacres, and of Operation Nemesis, in which several perpetrators of the Armenian genocide were assassinated.

With Sarkis Srentz, Haig Tiriakian (who assumed the name Hratch), and Max Zevrouz, he left Egypt and returned to the Ottoman Empire to participate in the efforts of the ARF.

[citation needed] After these events, Karekin Pastermadjian returned to Europe to continue his unfinished studies.

French Foreign Minister Gabriel Hanotaux declared the Armenians who had been connected with the Ottoman Bank Takeover as persona non grata and denied their stay in France.

When the Young Turk Revolution occurred in 1908, the Armenians in Erzurum, as well as the ARF, telegraphed Pastermadjian and asked him to become their candidate in the coming elections for Representative to the Ottoman Parliament.

Another fundamental object was to build those lines with American capital, which would make it possible to counteract the Russo-Franco-German policies and financial intrigues.

But in spite of all efforts unable to overcome the German, opposition in Constantinople, although, as the outcome of the struggle in connection with that bill, two ministers of public works were forced to resign their post.

Talaat, on behalf of the "Committee of Union and Progress", offered the portfolio of public works, refused these proposals, for the simple reason that he did not wish to compromise in any way with the leaders of the government.

[4] On 14 November, at the Bergmann Offensive, the second battalion of the Armenian volunteers engaged in battle for the first time, near Bayazid.

In the course of a bloody combat which lasted twenty-four hours, Dro, the commander of the battalion, was seriously wounded, and Garo was forced to immediately take his place.

[7] From that day until March of the following year, he remained at the head of that battalion, and led it into eleven battles in the neighborhood of Alashkert, Toutakh, and Malashkert, until Dro recovered and returned to resume the command.

He was elected to be ambassador of the First Republic of Armenia to the United States in Washington, D.C.[4] When the 1915 Armenian genocide broke out, Armen Garo became very depressed and sick.