When World War I broke out leading to confrontation between the Ottoman Empire and the Russian Empire in the Caucasus and Persian Campaigns, the new government in Istanbul began to look on the Armenians with distrust and suspicion. This was because the Imperial Russian Army contained a contingent of Armenian volunteers. On 24 April 1915, Armenian intellectuals were arrested by Ottoman authorities and, with the Tehcir Law (29 May 1915), eventually a large proportion of Armenians living in Anatolia perished in what has become known as the Armenian Genocide.