Differing views of what caused the Armenian genocide include explanations focusing on nationalism, religion, and wartime radicalization and continue to be debated among scholars. In the twenty-first century, focus has shifted to multicausal explanations. Most historians agree that the genocide was not premeditated before World War I, but the role of contingency, ideology, and long-term structural factors in causing the genocide continues to be discussed.

Historiography

Despite agreement about what happened during the Armenian genocide and who was responsible, there is still substantial differences of interpretation of the causes of the genocide and how it relates to prior anti-Armenian massacres. Bedross Der Matossian states that debates about cumulative radicalization, contingency, and premeditation are unanswerable until all archives, especially the Turkish ATASE archives, are opened to independent researchers. Different explanations of the genocide are not necessarily mutually exclusive. In the twenty-first century, research has shifted to focus on more nuanced, multicausal explanations. Many recent studies argue that the genocide was caused by a mixture of long-range and short-term factors, and balancing these has been central to the historiography. Studies also balance between objective causes as well as the subjective paranoia of the Committee of Union and Progress (CUP) leaders who ordered the genocide. Historian Hans-Lukas Kieser has highlighted the overlap between the regime's aims, stating, "Demographic policy, sovereignty issues and the safeguarding of a Turkish national home in Asia Minor were all closely linked."

The argument that the genocide was planned prior to World War I and that the war merely provided an opportunity to accomplish it—including such claims as the genocide being decided at the CUP's 1910 or 1911 congresses—predominated in early studies of the Armenian genocide but has since come to be discounted by most scholars. At the 1910 CUP congress, Mehmed Talat described non-Muslims as an "impenetrable barrier" to the desired "Ottomanizing [of] the Empire". Melson suggests that this could have been accomplished by means other than genocide, such as forced expulsion or assimilation. Bloxham and Göçek argue that although there was no plan for genocide before the war, "the future of the Armenians as a political community in the Ottoman Empire was very bleak". Historian Taner Akçam argues that "the Armenian genocide was less the product of wartime contingencies than of the empire's long-term structural problems".

Historians Donald Bloxham and Fatma Müge Göçek emphasize that understanding the underlying factors that led to genocide does not exonerate the leaders who chose it. Bloxham states that many Armenian genocide deniers have engaged in "abuse of context" in order to exculpate the Ottoman state. One line of argument, termed the "provocation thesis", holds that the genocide was an inevitable response to the provocations of Armenian revolutionaries, which are greatly exaggerated in such accounts. The international context has also been exaggerated to exonerate the CUP: for example considering the Armenians "victims of European diplomacy" or Ersal Yavi stating that the Armenians' fate was only because they were "in the pincers of European imperialism". A third line of reasoning accuses Armenians of siding economically with European imperialists to the detriment of Muslim Ottomans, disregarding contrary evidence. Pushed to its logical extreme, this argument justifies the expropriation, boycotts, and even deportation of Armenians as a form of national self-defense against the minority oppressor.

Religion and cultural explanations

Traditionally the Ottoman millet system offered non-Muslims a subordinate but protected place in society. The nineteenth-century Tanzimat reforms abolished the protections that members of the Armenian millet had previously enjoyed, but did not change the popular perception that they were different and inferior. In the 1890s, hundreds of thousands of Armenians were killed in the Hamidian massacres and in 1909, 17,000 were killed in the Adana massacre, and continued to be killed after World War I, during the Turkish War of Independence (1919–1923) despite vast differences in the ideology of the regime in power. One strand of historiography views the Armenian genocide as rooted in Islam or Ottoman culture and a continuation of these previous massacres.

Early studies on the genocide in Western scholarship focused on religion, particularly the work of Vahakn Dadrian, who argued that a "culture of violence" was inherent in the Ottoman theocratic system and that war only provided the opportunity for a genocide that CUP leaders already wanted to commit. Dadrian also argued that the Hamidian massacres were a less systematic precursor to the World War I genocide.

Donald Bloxham and Fatma Müge Göçek consider it "essentialist and therefore untenable" to blame the various anti-Armenian massacres on Islamic culture. Historian Ronald Grigor Suny and others have criticized this line of thinking, arguing that Dadrian fails to "explain why religion should have led to genocidal violence in the first year of the World War but not throughout Ottoman and Islamic history". According to historian Robert Melson, although elite motivations of enabling killing differed between the Hamidian massacres, Adana massacre, and Armenian genocide, there were always sufficient Ottoman Muslims willing to carry out the anti-Christian violence. He argues that such a predisposition for anti-Armenian violence already existed prior to 1915 and "it is probable that they were motivated by Ottoman and Muslim traditions of sectarian supremacy", among other potential motivations—but probably not nationalist ideology. On the other hand, Suny argues that genocide is initiated by an elite and requires popular acquiescence, but not necessarily active participation from the many as "a few killers can cause enormous destruction".

The 2019 book The Thirty-Year Genocide: Turkey's Destruction of Its Christian Minorities, 1894–1924 revived the focus on religion as a cause of genocide, and specifically arguments used by Dadrian, arguing that the Ottoman Empire and Turkish republic carried out a thirty-year-long genocidal project to replace Christians with Muslims in Anatolia. The book's conclusions have proved controversial among scholars. Reviewing the book, Mark Levene suggested that "the exterminatory violence of this period can be best explained not through a traditionally religious prism" but instead by the breakdown of the traditional millet system under the pressure of geopolitics and nationalism.

Territorial losses and refugee crisis

The Ottoman Empire lost sixty percent of its territory during the nineteenth century, followed by a loss of 80% of its European territory after the Balkan Wars. Such losses led to an opinion among the CUP that the empire was facing existential crisis.

Beginning in the mid-nineteenth century but especially after the Great Eastern Crisis in the mid-1870s, millions of Muslim refugees poured into the Ottoman Empire after being ethnically cleansed, mostly from the Caucasus and the Balkans. The Directorate for the Settlement of Tribes and Immigrants (IANM), which later played an important role organizing deportations during the Armenian genocide, was initially established to help resettle refugees from the Balkan Wars. Kieser and Bloxham state that the IANM and role of migrants as perpetrators indicate "some sort of transmission belt of anti-civilian, state-minority violence across boundaries". In the eyes of the CUP, Armenians bore collective guilt for the actions of Christians throughout the nineteenth century against the Ottoman state. Balkan Wars

Recapture of Edirne during the Second Balkan War was pushed by radicals within the CUP, especially Talat, and strengthened their faction. During the Balkan Wars, many ethnic Bulgarian and Greek soldiers in the Ottoman army defected. The stunning defeat led to a deep sense of national humiliation. Those Muslims who fled or were driven out of the Balkans were the raw material needed by the CUP to restructure the demographics of Anatolia in favor of Muslims. They were resettled on land expropriated from Christians who were killed or deported.

It is widely accepted that the Balkan Wars put an end to Ottomanism, the movement for pluralism and coexistence within the empire. Instead, the CUP turned to an increasingly radical ideology of Turkish nationalism to preserve the empire. Analogies with the Balkans led to an increasing anti-Armenian positioning within the CUP around 1913, as ethnic and religious pluralism was increasingly viewed as a dangerous liability. According to Bloxham and Göçek, although a causal connection between the Balkan Wars and the Armenian genocide is not proven, ethnic cleansing of Balkan Muslims may have provided a model for handling populations considered a problem.

Historian Uğur Ümit Üngör argues that "the involvement of seasoned criminals and militiamen hardened in years of (low-intensity) conflict in the Balkans, accounts for the cruelty of the genocide".

Armenian question

The Ottoman Empire lost the Russo-Turkish War of 1877–1878 and was forced to cede parts of the Balkans and Caucasus, as well as Ottoman Cyprus. At the 1878 Congress of Berlin, the Ottoman government agreed to carry out reforms and guarantee the physical safety of its Armenian subjects, but there was no enforcement mechanism; conditions continued to worsen. This marked the emergence of the Armenian question in international diplomacy as Armenians were for the first time used to interfere in Ottoman politics. Although Armenians had been called the "loyal millet" (millet-i sadıka) in contrast to Greeks and others who had previously challenged Ottoman rule, after 1878 Armenians became perceived as subversive and ungrateful.

Because of the territorial losses from the war, Sultan Abdul Hamid II decided that the Tanzimat reforms were a failure. Worried that they would lead to increased foreign influence or the creation of an autonomous region—as occurred in the Balkans—Abdul Hamid blocked the implementation of Armenian reforms. Instead, he focused on uniting the Muslims in the empire under pan-Islamic policies. Abdul Hamid created the Hamidiye regiments in the 1890s from Kurdish tribes; these were given free rein to commit violence against Armenians with impunity. In 1895, another European reform proposal was shelved after widespread anti-Armenian massacres that killed at least 80,000 Armenians. Akçam considers that "the Armenian genocide was driven by the traumatic memories of the nineteenth century's reform-massacre dynamic."