About 80% of the population is Turkish. The major ethnic minority (by mother tongue), the Kurds, is estimated at 20%. Arabs, Turkmen, Circassians, Greeks, and others do account for a small percentage of the population. Hundreds of thousands of Armenians were either killed or forced to flee during and immediately following World War I; bitterness between Armenians and Turks continues to this day, and during the late 1970s and early 1980s, Armenian terrorists took the lives of more than two dozen Turkish diplomats. The Greek component in Turkey was reduced as a result of the 1919–22 hostilities with Greece, the 1923 Treaty of Lausanne (which provided for an exchange of population with Greece), and the post–World War II Cyprus controversy. The Kurds, some of whom were forcibly dispersed after an uprising in 1935, still tend to be concentrated in the southeastern provinces. The Arabs live in the south along the Syrian and Iraqi frontiers, and the Greeks, Armenians, and Jews live in Istanbul and, to a lesser extent, in Izmir. Separatist Kurdish groups are outlawed, and there is a heavy military presence in the nine provinces where a state of emergency has been in effect since 1987.