The Bulgarian–Serbian wars of 917–924 were a series of conflicts fought between the Bulgarian Empire and the Principality of Serbia as a part of the greater Byzantine–Bulgarian war of 913–927. After the Byzantine army was annihilated by the Bulgarians in the battle of Achelous, the Byzantine diplomacy incited the Principality of Serbia to attack Bulgaria from the west. The Bulgarians dealt with that threat and replaced the Serbian prince with a protégé of their own. In the following years the two empires competed for control over Serbia. In 924 the Serbs rose again, ambushed and defeated a small Bulgarian army. That turn of events provoked a major retaliatory campaign that ended with the annexation of Serbia in the end of the same year. The Bulgarian advance in the Western Balkans were checked by the Croats who defeated a Bulgarian army in 926.