https://en.wikipedia.org/wiki/Armenian_Genocide
The genocide began long before WWI.
It began as soon as Sharia was implemented.
The preceding form of governance --- the Ottoman millet system --- oppressed the Christian Armenians (and Jews and other non-Muslims) in a terrible manner for 400+ years, but they were able to survive and even grow in numbers under the usual protection racket, as dhimmis. The actual, formal, systematic genocide didn't ensue until the more "modern" nationalists took over (late 19h century, Young Turks etc.).
The dhimmi-millet and the sharia-genocide are both hell-bent, damnable Islamic systems. The difference is, under dhimmitude the despised, victimized Armenians could survive for 400 years; in contrast, a couple eruptions of genocide-massacres, and the Armenians were absolutely wiped out. First "hecatomb", first "holocaust" of the 20th century.