 Complete the following phrase:  After the emergence of rival national movements among Balkan Christians, the allegiance of Macedonian Slavs became the apple of discord for nationalists vying for dominion over the region of Macedonia. Parties with national affiliations, mostly Greek and Bulgarian, were formed in their midst, largely expressing and accentuating pre-existing social cleavages. From the 1870s onwards Bulgarian and Greek propaganda appealed to them via the creation and operation of national education networks and by supporting the structures of the Bulgarian Exarchate or the Patriarchate of Constantinople respectively. Amidst worsening economic and political conditions for Slav peasants, the clandestine Internal Macedonian Revolutionary Organization, founded in 1893, gained a wide following with a program of agrarian reform imposed by terror, culminating in the staging of the Ilinden uprising of 1903, which was swiftly suppressed by the Ottomans. An 