There was a war by the name of Domitian's Dacian War where a conflict was brought between the Roman Empire and Dacia when the province of Moesia was invaded. The war was under Roman emperor Domitian's reign and took place between 86-88 AD.
Defeat of Oppius Sabinus[]
When 85 AD ended and somewhat in the beginning of 86 AD, Dacian king Duras decided to tell his troops to attack the Roman province of Moesia which was on the south of the Danube river. There, the Dacian army was led by Diurpaneus and often cited as one and same with the later king titled Decebalus. Even though the assumptions remain obscurely founded and problematic, it seems that Romans were caught by surprise, when the governor Oppius Sabinus and one of the legions most likely to be Legio V Alaudae were eventually killed.
When the attack occurred, Emperor Domitian of the Roman Empire who was with Cornelius Fuscus, one of the Praetorian Guards arrived personally in Moesia, then they reorganized the province into Moesia Inferior and Moesia Superior then they planned a attack in the future to invade Dacia. They tried to replace the lost legion and strengthen the Roman army at that section even greater then before then Legio IIII Flavia from Dalmatia and two other legions, Legio I Adiutrix and Legio II Adiutrix who were from western provinces came to Moesia. Then, the region of Sirmium was attached with Moesia Superior so they can have a single command over the Dacian frontier.
Historians divide as to what happened next, one of them say that after handing over the command to Fuscus, Domitian returned to Rome in the same year while Fuscus cleared of Dacian invaders from the province and according to two other historians, they say Domitian led the operation successfully and returned to Rome to celebrate their victory.
Cornelius Fuscus's Defeat[]
During the same year of 85 AD, the initial success against Dacians happened and Cornelius Fuscus crossed over to the Danube but, his army was suddenly ambushed and destroyed while Fuscus himself was killed in battle and according to other historians, this is the battle where Legio V Alaudae was attacked and killed. The legion randomly disappeared from the list of the Roman armies.
Soon, after that victory Diurpaneus got the name of Decebalus which meant as strong as ten wild men.
Peace[]
When the battle ended, course of events were unclear. Suetonius mentioned that several battles varied success against the Dacians and Lucius Antonius Saturninus who was commander of the Roman army in Germania Superior eventually revolted. Then, Iazyges, Marcomanni, and Quadi refused to provide troops to Domitian for the Dacian war he was entering. Domitian then killed their peace emissaries and attacked them after that, he left for Rhine. He was eventually forced to return to Pannonia after Romans suffered a loss there and all the problems halted the Roman offensive and Decebalus who was now Dacian king, sued for peace, when he sent his brother Diegis as his plenary representative. Then under terms of the treaty, Decebalus returned Roman prisoners of war and he was also lent a number of Roman engineers help him in building defensive fortifications. The Romans would also pay an annual subsidy of 8 million sesterces and Decebalus was recognized as the client king of Rome.
Aftermath[]
Then the remainder of Domitian's reign, Dacia remained a peaceful kingdom and Decebalus used all of the Roman money to fortify his defenses. Domitian also wanted a new war against Dacians and reinforced Upper Moesia with two cavalry units who were brought from Syria and at-least five cohorts brought from Pannonia. Trajan also continued Domitian's policy and added even two more units to the auxiliary forces of Upper Moesia, then soon he used the buildup of troops for his soon to come Dacian wars.