War was result of chain of uprisings against Ottomans in Balkan Peninsula.
Russia always wanted to occupy Balkans, so they promised military assistance in order to expand it's Empire. To Russians - they were heir of Byzantium Empire and wanted to capture Constantinople.
On the other hand, nations of Balkans made alliances with different countries, but international politics was very complex. It all depended on Napoleon and France. Russians were allied with Turkey when Napoleon was fighting against them in Egypt, and changed sides many times.
Back to Balkan states - south of Danube and Sava rivers there was nothing but armed civilians with few uniformed units. 2/3 of modern Romania (Transylvania and Romanian Banat) were part of Hapsburg Empire, as was Croatia and north of Serbia (now Serbian Banat). There you can find respectful armed units such as Grenz infantry, Dragoons and Hussars. In most cases line infantry was made of German minority (or majority in some ares, especially Serbian Banat), Hussars were Hungarian or Sekely, Dragoons were Romanians, while light infantry was made of Yugoslavs...
Talking of people from Balkan (south of Danube and Sava rivers) they wore 'Turkish' stile civilian clothing (minus turban, if they were Christians) and had few very small military detachments (of regular infantry) clothed in French, Russian and Austrian uniforms.
It all is very confusing as all these countries changes sides very often. Turkey itself was in a sort of civil war at the time...
I wonder if it gives any clue?
Germans from Banat-