McCarthy's studies concentrate on the period in which the Ottoman Empire crumbled and eventually fell apart. McCarthy believes that orthodox Western histories of the declining Ottoman Empire are biased, since they are based on the testimonies of biased observers: Christian missionaries, and officials of (Christian) nations who were at war with the Ottomans during World War I. Able to read Ottoman Turkish, he focuses on changes in the ethnic composition of local populations. Thus, he has written about the ethnic cleansing of Muslims from the Balkans and the Caucasus, as well as the Armenian massacres in Anatolia. Scholarly critics of McCarthy acknowledge that his research on Muslim civilian casualties and refugee numbers (19th and early 20th centuries) has brought forth a valuable perspective, previously neglected in the Christian West: that millions of Muslims and Jews also suffered and died during these years. Donald W. Bleacher, though acknowledging that McCarthy is pro-Turkish nonetheless has called "Death and Exile" "a necessary corrective" challenging the West's model of all victims being Christians and all perpetrators as being Muslims.