|Carolingian Union|| Braniches †
|Commanders and leaders|
| Pepin of Italy|| (Bulgaria) Krum †
Several war chiefs
|Casualties and losses|
The Unification Wars were a series of wars led by the Carolingian Union, composed of the Eastern Roman Empire and the Frankish Empire, against the Balkan Slavs to unite the armies of Francia and Byzantium under a common goal. The war was costly to both sides, especially the Slavs, though the casualties against the Carolingian Union had mainly occurred at the hands of the Bulgarians under Krum.
The Eastern Roman Empire had grown highly alienated from their cousins in the west. As their cultures grew apart, the goals of the Eastern and Western powers began to counteract, bringing the Byzantine Empire and the western nations into conflict, generally via proxy wars. Irene and Charlemagne's marriage unified two nations that were unwilling to work together.
In an effort to work out the issues between the Franks and the Byzantines, Irene and Charlemagne decided it would be good for both parties if they limited their power over the other. They created goals that were beneficial to the other nation, if not the same as the other nation. While the changes took place, Charlemagne and Irene decided that it was time to invade the Balkans, an area that had given the two nations trouble in the past.
The war was not particularly well-documented, though several battles that showed the Franks and the Byzantines working together were described to historians on either side. What is known is that the Franks made the first move by invading Braniches territory in 806. The Byzantines then invaded northern Dragovit territory, flanking the Dragovit and Zagorechian territory. The initial battles went well, with the Dragovits and Zagorechians surrendering by 810. Unfortunately, Irene of Athens died at this time. Charlemagne was forced to rule over both the Byzantine and Frankish Empires, dealing a blow to the morale of the Byzantines.
The war on the Frankish side, however, was complicated when the Croats revolted against the Franks upon hearing the news of the invasion of the Braniches. The Croats slowed the Franks down and incited revolts in the Braniches against the Frankish occupation. It wasn't until 814, less than a month before Charlemagne's death, that the Croat rebellion was put down and the Franks were able to make significant gains in the Balkan area. By 817, the Croats were annexed by the Franks and became a client state once again.
While the Franks were caught up with the various rebellions in the Balkan area, the Byzantines were invading Dioclea. The invasion, beginning in 811, was an invasion of Dioclea's southern borders as well as an invasion from the coast. The Diocleans quickly yielded, giving up the fight by 814. The Serbs were next on the chopping block. A massive invasion from their southern and western borders almost immediately overwhelmed them, but the Bulgarians took the opportunity to invade the Byzantines, defeating them in the Struma valley and carving out massive swaths of territory.
Upon the death of Charlemagne, Pepin of Italy needed to go to the Byzantine Empire to become Emperor, forcing him to leave his armies as they were fighting the Croats. As leader of the Byzantine forces, he immediately rejoined the fight, turning the tide against the Bulgarian king, Krum. Before long, in 818, an assault into Pliska. Krum himself died in the fighting. According to a noted historian, Pepin himself had landed the killing blow, but modern historians refute this claim, stating that it is likely that this statement was a fabrication in order to raise morale. After the Battle of Pliska, the Bulgarians sued for peace. Pepin accepted the truce and returned Pliska in return for a tribute to be paid to the Byzantine Empire every year.
After 818, the Byzantines and Franks returned their attention to the remaining states left opposing them. By 831, the resistances had died down, with the final battle being at Ras. According to several historian, the Frankish and Byzantine armies had never met until the Battle of Ras. This claim is refuted by modern historians, who state that the armies had met several times before, but the Battle of Ras was the only major battle in which they participated. Nevertheless, there was allegedly a massive celebration in Ras by the two armies. Whether or not this actually happened is debated upon; it is argued by some historians that the celebration was a fabrication to boost the morale of the armies. The other side, however, believes that this celebration took place, though to which extent is unknown.
The Unification War did what it was supposed to do; it brought the Byzantine and Frankish armies together, making people from both countries believe that the two nations were fighting for the same thing. By the time this war ended, Frankish opinions of the Byzantine had vastly improved and vice versa. The Unification War was a very important step in the unification of the Byzantine and Frankish Empires and in the rectification of the issues between eastern and western Europe.
The territory gained in the Unification War later went on to compose the themes of Croatia, Serbia, and Slavia in the Carolingian Union.