After two years of studying at the university's faculty of law, he left Saint Petersburg and returned to the Caucasus in order to participate in the Armenian national movement against the Ottoman Empire.

In 1906, Nzhdeh moved to Bulgaria, where he completed his education at the Dmitry Nikolov Military College of Sofia and in 1907 received a commission in the Bulgarian army with the rank of lieutenant.

In 1912, together with General Andranik Ozanian, he joined a battalion of ethnic Armenians within the Macedonian-Adrianopolitan Volunteer Corps of the Bulgarian army to fight against the Ottoman Empire in the Balkan wars, partaking in the campaigns to seize Thrace and Macedonia.

After clashing with Ottoman forces in Alexandropol, the Armenian fighters led by Nzhdeh dug in and built fortifications in Karakilisa (moder-day Vanadzor).

He managed to mobilize a population of demoralized locals and refugees for the coming fight through his inspiring speech in the Dilijan church courtyard, where he called on the Armenians to wage a sacred battle: "Straight to the frontline, our salvation is there".

[16] In April 1920, Nzhdeh led his troops from Kapan to Mountainous Karabakh's southern district of Dizak, soon after the massacre of the Armenian population of Shushi.

Their intervention, along with pressure on the Azerbaijani authorities from the Entente powers, brought an end to the massacres of the Armenian population of Mountainous Karabakh.

On 24 May 1920, Dro, Nzhdeh, Colonel Dmitri Mirimanyan and ARF representative Arsen Mikayelyan agreed to withdraw from Karabakh and hand over power in the region to local Armenian Bolsheviks led by Sargis Hambardzumyan.

[19] In August 1920, Nzhdeh refused orders from Minister of Defense Ruben Ter Minasian to leave Kapan and come to Yerevan in accordance with an agreement reached with Soviet Russia to allow the Red Army to enter Zangezur (Syunik), Karabakh and Nakhichevan.

[19] In January 1920, Nzhdeh's partisans, aggravated by the massacre of Armenians at Akulis, "wiped out" 9 villages and 40 hamlets southeast of Goris – the continued attacks on Azerbaijani Muslim settlements led Azerbaijan to reposition its forces towards Zangezur again after their unsuccessful campaign in November 1919.

[19] Between April and July 1921, the Red Army conducted massive military operations in the region, attacking Syunik from north and the east.

After the conflict, Nzhdeh, his soldiers, and many prominent Armenian intellectuals, including leaders of the first independent Republic of Armenia, crossed the border into the neighboring Iranian city of Tabriz.

[19] The ARF Bureau, in particular leading members Ruben Ter Minasian and Simon Vratsian, expressed its desire to establish relations with Turkey, while Nzhdeh and others such as Shahan Natalie believed that the party should maintain a strictly anti-Turkish orientation.

He was summoned by the party to Cairo in 1937, where the ARF Bureau unsuccessfully attempted to resolve its differences with Nzhdeh and reconcile him with Ruben Ter Minasian.

[26] Operation Gertrud, a joint German-Bulgarian project about attacking Turkey in the event that Ankara joined the allies, was discussed in Berlin.

[24] That year the Nazis created the Armenische Legion, composed mostly of captured Soviet Armenian prisoners of war, and placed it under the command of veteran ARF leader Drastamat Kanayan.

[24] Together with Artashes Abeghyan and Abraham Gyulkhandanyan, Nzhdeh co-edited and wrote for Azat Hayastan ("Free Armenia"), the pro-German and anti-Soviet organ of the Armenian National Council, which published only two issues in 1943.

[32] After receiving a telegram from the Soviet authorities announcing his death, Nzhdeh's brother Levon left Yerevan for Vladimir to take care of his burial service.

This was done through the efforts of Pavel Ananyan, the husband of Nzhdeh's granddaughter, with the help of linguistics professor Varag Arakelyan and others, including Gurgen Armaghanyan, Garegin Mkhitaryan, Artsakh Buniatyan, and Zhora Barseghyan.

According to the participants of the funeral, the rest of Nzhdeh's body was kept in the cellar of Varag Arakelyan's house in the village of Kotayk until 9 May 1987, when it was secretly transferred to Vayots Dzor and buried in the churchyard of the 14th-century Spitakavor Surb Astvatsatsin Church near Yeghegnadzor.

After Israeli ambassador Joel Lion denounced a small rally "glorifying" Nzhdeh and called him a "Nazi collaborator" in January 2024,[38] Armenia's Foreign Ministry criticized him for "exploiting" actions based on national and religious intolerance.

[39] In 1923, while in Bucharest, Romania, Nzhdeh published a series of articles in the local Armenian newspaper Nor Arshaluys ("New Sunrise") entitled "My word - Why did I take up arms against the Soviet troops?"

Nzhdeh wrote in detail about the history of the wars in Syunik (Zangezour) in an extensive series of articles for the Boston newspaper Hairenik ("Homeland") in 1923–1925.

[40] In 1926, Nzhdeh wrote for the newspaper Araks based in Sofia, Bulgaria, where he published a series of articles titled "Open Letters to the Armenian Intellectuals".