Ivan Shishman declared independence in 1378 following the death of Nikephoras IV "Purple Born". Led by an army of 20,000 Bulgars they attempted to revolt against the Byzantine empire following the internal strife with the Byzantine empire. Hoping to restore the once glorious Empire of the Bulgars, they marched on Tarnova and the local garrison surrendered without a fight
Invasion from Nicaea in 1380 CE
With John IV "The Nicene" capturing Constantinople, soon John marched with an army of 25,000 men to subdue the land of the bulgars, however it was stopped and John's army retreated to Hadrianople with 15,000 men, to which John transferred 10,000 men to Nicaea to link with other troops campaigning against Trebizond.
With a successful victory Ivan captured many towns solidifying his hold on the Diocese of Thracia but he was beginning to lose control of the Diocese of Bulgaria.
Andronikos IV's invasion and fall in 1384 CE
While John IV fortified Constantinople and tried to strengthen his position in Thracia, Andronikos IV had led troops to capture Ivan's western most city of Messembria while Basil III led troops from the Diocese of Dyrrichion and the Exarchate of Sicily. Ivan soon withdrew from Thracia to attack the Byzantines. However, when chasing the Byzantine navy, the fleet was annihilated by Greek fire and the rest of the ships were captured.
Basil III was hot on his tail and he retreated Varna. From their he made his final stand with only 3,000 men. However while fighting he was killed by Greek fire and with it the last glory of Bulgaria vanished