Thanks for the heads up.
The history of modern bulgarian identity starts with the exarchy – these guys: https://en.wikipedia.org/wiki/Bulgarian_Exarchate

The Ottomans made no official distinction between their christian subjects, so our bishops were appointed by the patriarch in Constantinople and the liturgy was in Greek (which was incomprehensible to the majority of the slavic speaking population). As the saying went, the Turk seeks to enslave your body, but the Greek will enslave your soul. Not only that, but the whole system was corrupt and positions were being sold to opportunists with no theological credentials who then recouped their losses by fleecing the believers – these guys https://en.wikipedia.org/wiki/Phanariotes.

This led to this guy https://en.wikipedia.org/wiki/Paisius_of_Hilendar writing his history-manifesto called “История Славяноболгарская”, which started a process that ended with a census which gave religious authonomy to all dioceses where at least 2/3rds of the population identified as Bulgarian (not Serbian or generally Slavic). The results are visible on the map in the first link.

When Bulgaria was liberated in 1878 it comprised more or less those same territories, however, shortly thereafter it was partitioned at the Berlin Congress into the Princedom of Bulgaria (ottoman vassal), Eastern Rumelia (autonomous province) and Macedonia, which remained a part of the Ottoman Empire.

Shortly thereafter Bulgaria annexed Eastern Rumelia (good thing too, or we’d have Ancient Thracia to the south, probably) and we would’ve annexed Macedonia too, if it wasn’t for our pesky  allies in the Balkan wars, who reneged on their pre-war agreements and decided to keep all of the occupied territories for themselves. See, Serbia and Greece fought mostly on the Macedonian front while Bulgaria mostly on the Constantinople front so Serbia and Greece ended up with territories populated by mostly Bulgarians and we ended up with more Turks. The King kind of jumped the gun and declared war on Serbia and Greece, which Romania and the Ottomans joined because why not. Long story short, the pussies in in the government in Sofia got scared and sued for peace. So we lost more territory. A couple of years later a similar situation occurred in WWI and then again in WWII.

Greece either thoroughly ethnically cleansed the bulgarian population or assimilated them. (So did the Turks, but that was kind of expected). The Serbs would have assimilated them too if not for Tito, Stalin and the Comintern who decided to create a separate Macedonian identity instead (no idea if that was before or after their disagreement). There was also an effort to force macedonian Bulgarians to declare themselves “ancient macedonians” in Bulgaria proper. Had they succeeded it would’ve been interesting if Stalin would’ve partitioned Yugoslavia to create an “independent” Macedonia. There might be some justfication for the whole greek paranoia over “muh territores” (which they repopulated with Greeks from Asia Minor but that’s another story). The modern macedonian ruling class is comprised of the same communist apparatchiks of yugo times so they are unerstandably hostile to Bulgaria. This you can personally experience if you decide to cross Macedonia in a car with bulgarian registration, if you’re curious

You owe me a beer now.