Battle of Kupa
The Battle of Kupa occurred at Kupa river in 819. It involved Frankish vassal Duke Borna of Duchy of [Littoral Croatia|Littoral Croatia], with an army of Guduscani, against the advancing army of Frankish rebel, Duke Ljudevit of Slavs in [Lower Pannonia|Pannonian Croatia]. During the battle, the Guduscans abandoned Borna and joined Ljudevit. While Borna's forces suffered massive losses, he managed to escape with his bodyguards. However, Dragomuž, Ljudevit's father-in-law, who sided with Borna, was killed. Ljudevit suffered heavy casualties that included 3,000 soldiers and over 300 horses. Afterwards, Ljudevit used the momentum to invade Littoral Croatia in December 819.