TLDR: Ottomans reforms in the mid 19th century gives non-Muslims more rights leading to more education about the national identity of the Armenians. Armenians seek autonomy from Turkey in the aftermath of the Russo-Turkish war bringing the 'Armenian Question' into the minds of Europeans. The Congress of Berlin decided the Ottomans must grant autonomy to the Armenians but never put a way to force them to do so. Anti-Armenian sentiment is on the rise due to the rise of Turkish Nationalism leading to the Hamidian Massacres of the 1890s and the Adana massacre in 1909 leading to an active independence struggle for the Armenian people in the Ottoman Empire. So to answer your question, the Armenians have been taking anti-Ottoman activities (in the narrowest sense) since the Reforms of the 19th century.

During the Tanzimat Reforms of the Ottoman empire and as a result of diplomatic pressures on the Ottoman Empire by its allies during the Crimean War, what you see is the Ottoman Empire being forced to give non-muslims the same rights as Muslim citizens. This leads to the abolition of the jizya tax on non-muslims, allowing for non-muslims to be come soldiers and most importantly allowing for the opening of non-muslim schools. These reforms change the balance of power from the Church controlled millet system into a secularized leadership. Many Armenian schools were opened during this time and adopted a secular identity. In the wake of Ottoman Defeat in the Russo-Turkish War, Armenians of the Ottoman Empire send a delegation to the Congress of Berlin to represent Armenians starting a debate in Western Europe known as the "Armenian Question." Effectively what this asks for is a 'national awakening' of Armenians similar to what happened in Bulgaria resulting in the self-determination of Armenians. The Congress of Berlin mentions the possibility of autonomy in Armenia turning the issue from domestic to international but the Congress of Berlin did not necessarily force the Turks to make any reforms.

With the rise of both Armenian nationalism and Turkish nationalism at the same times, the Ottomans see a surge of anti-Armenian sentiment. Armenian revolutionaries have fought for the self-determination of Armenians for much of the late 19th century. Prior to the genocide of 1915 there was two other genocidal massacres on Armenans including the Hamidian massacres of 1894-96 and the Adana Massacre of 1909. The Hamidian massacres in particular begin a wave of revolutionary sentiment in the Armenian region of the Ottoman Empire asking for complete independence and self determination of the Armenian people. These two instances of genocide are often ignored by the Turks as it gives legitimacy to Armenians demanding independence during the First World War and defending themselves against Ottoman Soldiers. With Germany growing close with the Ottomans, the Russian empire became more interested in the welfare of Armenians in the Ottoman empire (as there are also Armenians living in Russia.) During the Armenian Genocide, an autonomous Armenian Government, named the Republic of Van, was set up in the Vaspurakan region. This government was eventually pushed back by the Ottomans being pushed into Russia and refugees from the Turkish Massacre soon followed. Following the February Revolution in Russia there was hope amongst Russian Armenians and Armenian Refugees that the Russians would help seize Ottoman Armenia for them. Russian support ended following the Bolshevik revolution leading to the formation of the country of Transcaucasia which broke apart within a month. Following the independence of Armenia they fought wars with both Georgia and Azerbaijan, in the Aftermath of World War I what you see is a conflict between Turkey (during the Turkish Independence) war against the Armenians. The results of the war established the modern borders of Armenia and Turkey.