Herennius Etruscus was the elder son of Emperor Decius and ruled from May to June 251 CE. From the beginning of the reign of Herennius, the gothic tribes (under the so-called Kniva) crossed the Danube and looted Moesia and Dacia. An expedition of 20,000 Romans was organized against the invaders, in which father and son took part.
The Roman army surprised the Goths when they were returning to their lands with the spoils from the expedition. However, the great commanding powers of the Goth chief let him take the initiative. The battle of Abrittus started. Kniva, outnumbering the Romans, divided his forces into smaller and more mobile units, trying to draw the Romans to the marshlands. The guests were lined up in three lines, where the last one was to surround the army of Decius in the swamps. The Romans attacked from the front.
They managed to break the two lines of the Goths, but in the attack of Decius was killed the son of the Emperor, who was hit with an arrow. After pulling the Romans into the swamp, the Goths surrounded the enemy and crashed it completely. Emperor Decius died with almost the entire army. This was the first time that two emperors perished during a battle with a foreign invader. Estimated for less than a thousand peoplesurvived and withdraw under command of Trebonianus Gallus, who was immediately acclaimed as the new ruler. Trebonianus accepted the conditions of the Goths, who were allowed to withdraw with all their loot. In addition, he undertook to pay the annual tribute in exchange for the Goths respect of the Roman border on the Danube.