Orthodoxy and Nationalism
Unfortunately, it is a common misconception to link Orthodox Christianity with nationalism.
Nationalism, a product of Western Europe, began in the eighteenth century with the French revolution. This revolution brought radical new ideas that paved the way for the modern nation-state, and with it came the ideas that brought the inevitable decline and fall of the Ottoman Empire.
Specifically, notions of romantic nationalism from the French Revolution were carried to Eastern Europe. This caused the disintegration to the Ottoman millet system, a system of administration which the empire never found an alternative for.
Those living under the Ottoman Empire were bound by religious, linguistic, and cultural affiliations. The Western notion of citizenship was practically non-existent, and ethnic origin was also considered relatively unimportant. Under this system, religious hierarchs that appealed to certain linguistic groups such as the Greek Orthodox Patriarch of Constantinople reported directly to the Sultan of the Ottoman Empire. From the fourth century onward, a Christianized Roman culture had developed that the Turks had never been able to destroy.
It is because of this that the struggle for political freedom erupted under these Christian hierarchs, first by the Serbians and then by the Rhomaioi (Greeks). In the century that followed the revolutions of the Serbians and the Rhomaioi, a wave of national awakening erupted across the entire Ottoman Empire. At the same time, it is important to note that nationalism has had little to do with Orthodoxy as it is the product of secular philosophies that had developed in Western Europe.
Many Christian ideas, as they pertain to spiritual salvation, have historically often at odds with secular ideologies such as nationalism. For example, when Greece first became independent it had a German monarch, German architecture, and the German idea of Church-State relations. The Orthodox Church of Greece was established as autocephalous, without reference to Constantinople, and where the Patriarchs had initially opposed it due to Ottoman pressure in Constantinople.