A couple years ago, I included information about the Armenian genocide during WWI in my modern history curriculum. Only recently, when I was reading Turkish Reflections, did I realize that the information I had was pretty one-sided. The Turks probably didn't just, one day, decide to kill all the Armenians because they wanted the land; rather, it was the latest in a centuries-long conflict between the two groups. Unfortunately, it is still hard to get accurate information easily, so figuring out what happened is more a matter of balancing biased accounts rather than finding an unbiased source.
According to Wikipedia, the Armenians have been a nation since roughly 190 BCE; they have had several independent kingdoms, interspersed with rule by Persians, Byzantines, Seljuks, and Ottomans.
So far, I know that the Armenian-Turkish conflict goes back to before the First Crusade, in 1097, when some Norman Crusaders broke away from the main army and tried to set up an independent Armenian state in Anatolia. The Armenians at first welcomed the Normans as liberators who would free them from the tyranny of the Byzantines and the Turks, but then figured out that the Normans were only interested in setting themselves up as rulers for the status (and money) it would bring. At least this far back, there was conflict between the Turks and the Armenians; it probably goes back to 1071, when the Muslim Turks beat the Byzantine army at Manzikert and took over rule of Anatolia, including the Christian Armenians.
I am reasonably sure that nine centuries of intermittent conflict later, the Russians were encouraging the Armenians to break free of the declining Ottoman Empire and set up an independent Republic of Armenia; since this was occurring during WWI and the Turks were on the other side of the war, it isn't surprising that they considered it treason and took action to stop it, including moving all Armenians out of Anatolia, on forced marches, to the desert near the coast. On the other hand, the Ottoman Empire had been fighting Armenians since 1894-6, and might have used the Russian connection as a pretext for the mass deportations. According to Wikipedia, "The events of 1915 to 1923 are regarded by Armenians and the vast majority of Western historians to have been state-sponsored mass killings. Turkish authorities, however, maintain that the deaths were the result of a civil war coupled with disease and famine, with casualties incurred by both sides." (But who wrote the entry? It refers to the "Ottoman yoke", so it isn't unbiased.) It is hard to find out what really happened; it couldn't have been as one-sided as many of the Armenian websites claim, if for no other reason than that life is seldom that simple. The truth may never be known, even approximately - which makes it really hard to incorporate into my modern history curriculum.