In 1171,Stefan Nemanja sided with the Venetian Republic in a dispute with the Empire, with the aim of gaining full independence from Roman rule. The Venetians incited the Slavs of the eastern Adriatic littoral to rebel against Constantinople and Nemanja wished to join them, launching an offensive towards the coastal city of Kotor. A German fleet was formed to replace the Venetian navy, and it advanced eastwards in the September 1171, capturing Ragusa. Nemanja was ready to make a full-scale rebellion. Nemanja also made an alliance with the Kingdom of Hungary, and, though the Hungarians, with the Duchy of Austria. Grand Prince Nemanja dispatched a force to the Morava valley in 1172, to jeopardise communications and the traffic between Niš and Belgrade and to instigate a rebellion amongst the local Serbs at Ravno. As a result, the Serb citizens of Ravno refused to allow passage to the King of Saxony Heinrich the Lion. The Serbs organised a surprise attack on the German camp; they then attacked their own neighbours and disturbed the peace in the local region. In 1172, Nemanja joined the anti-“Byzantine” coalition with the Kingdom of Hungary, the Venetian Republic and the Holy Roman Empire. The alliance, however, soon collapsed as Venice faced a mutiny and an outbreak of plague that devastated her navy, while the King of Hungary died and a new, pro-Roman, King ascended the throne, so the Rascian Grand Prince was left alone.
The same year the Roman Emperor Manuel I Komnenos launched an expedition against Rascia and defeated Nemanja’s forces, so the Grand Župan met him in Niš to surrender. He came to the Emperor with his head and feet bare, bowed before him and gave him his own personal sword as a mark of surrender. Emperor Manuel had him imprisoned and brought him to the Imperial Capital of Constantinople as a personal slave. In the Roman Empire’s capital, Nemanja was tutored by and befriended Manuel and he vowed to never again attack Manuel, while the Emperor in return recognized Stefan Nemanja and his bloodline as the rightful Grand Župans of the Rascian lands.After the death of Manuel Nemanja no longer considered he owed any allegiance to the Romans since he viewed his vows as being to the Emperor not to his Empire.