Decebalus (ruled 87-106 A.D.) (Decebal in Romanian) was a Dacian king.
After the death of Great King Burebista, Dacia split into four or five small states. The situation continued until Decebalus managed to consolidate the core of Dacia around Sarmizegetusa in today Hunedoara district (in Romania). He reorganized the Dacian army and in 85 the Dacians began raiding the heavily fortified Roman province of Moesia, located south of the Danube.
Domitian decided to send his prefect of the Praetorian Guards, Cornelius Fuscus, to punish and conquer the Dacians, but the two Roman legions sent were defeated and their battle standards were captured by the Dacians.
Another attack on Dacia, in 88, was successful, but revolts of the Germans on the Rhine required the military force of Moesia, and the Romans were forced to pay large sums of money in the form of Tribute to the Dacians for maintaining peace in this region. The humiliating situation for the Romans lasted until Trajan acceded as Emperor of the Roman Empire in 98. Immediately he engaged in a series of military campaigns which would expand the Roman Empire to its maximum extent.
Decebalus was defeated by the Romans when they invaded Dacia in 102, but he was left as a client king under a Roman protectorate. Three years later, Decebalus destroyed the Roman troops in Dacia, and the Romans were forced to send reinforcements.
After a long siege of Sarmizegetusa and a long battle, the Romans conquered Dacia. After his army was defeated, rather than being captured as a prisoner by the Roman soldiers, Decebalus committed suicide.