Domitian ' s Dacian War Domitian ' s Dacian War was a conflict between the Roman Empire and the Dacian Kingdom , which had invaded the province of Moesia . The war occurred during the reign of the Roman emperor Domitian , in the years 86 – 88 AD . The Dacian attack in 86 and the defeat of Oppius Sabinus . At the end of 85 or the beginning of 86 AD , the Dacian king Duras ordered his troops to attack the Roman province of Moesia on the southern course of the Danube river . The Dacian army was led by Diurpaneus , the later king Decebalus . It seems that Romans were caught by surprise , since the governor Oppius Sabinus and a legion , probably the V Alaudae , were annihilated . Following this attack , the Roman emperor Domitian , accompanied by Cornelius Fuscus , Prefect of the Praetorian Guard , personally arrived in Moesia , reorganized the province into Moesia Inferior and Moesia Superior , and planned a future attack into Dacia . To replace the lost legion and greatly strengthen the Roman army at this section , the IIII Flavia from Dalmatia and two more legions , the I and II Adiutrix , from western provinces were moved to Moesia . The region of Sirmium was attached to Moesia Superior , in order to have a single command over the endangered Dacian frontier . Historians are divided as to what happened next . A . Mócsy suggests that after handing over the command to Fuscus , Domitian returned to Rome in the same year , while Fuscus cleared the Dacian invaders from the province . According to E . T . Salmon and M . Bunson , however , Domitian personally led the successful operations then he returned to Rome to celebrate a double triumph . The defeat of Cornelius Fuscus . In the same year ( 86 ) , after the initial success against Dacians , Cornelius Fuscus crossed the Danube . However , his army was ambushed and destroyed while Fuscus himself died in the battle . According to E . T . Salmon and other historians , this was the battle where Legio V Alaudae was annihilated . At any case , this legion subsequently disappeared from the Roman army list . After this victory , Diurpaneus received the name of Decebalus , meaning as strong as ten wild men . The battle of Tapae . The Roman offensive continued the following year , with general Tettius Iulianus now in command . The Roman army entered Dacia , advancing from Viminacium towards the Iron Gate Pass . The battle took place at Tapae , in 88 AD , but this time the outcome was a Roman victory . Peace . After the battle , the course of events is unclear and a satisfactory chronological reconstruction is not possible . Suetonius mentions that there were " several battles of varying success " ( against the Dacians ) . Lucius Antonius Saturninus , commander of the Roman army in Germania Superior , revolted . In addition , Iazyges , Marcomanni and Quadi refused to provide troops to Domitian for his Dacian war . Domitian killed their peace emissaries and attacked them , then he left for Rhine . He was forced to return to Pannonia after the Romans had suffered a defeat there . All these problems halted the Roman offensive and Decebalus , now the Dacian king , sued for peace , sending his brother , Diegis , as his plenary representative . Under the terms of the treaty , Decebalus returned the Roman prisoners of war but he was also lent a number of Roman engineers who helped him in building defensive fortifications . The Romans would pay an annual subsidy of 8 million sesterce s and Decebalus was recognized as a client king of Rome . Aftermath . For the remainder of Domitian ' s reign Dacia remained a relatively peaceful client kingdom , but Decebalus used the Roman money to fortify his defences . Domitian probably wanted a new war against Dacians , and reinforced Upper Moesia with two more cavalry units brought from Syria and with at least five cohorts brought from Pannonia . Trajan continued Domitian ' s policy and added two more units to the auxiliary forces of Upper Moesia , and then he used the build up of troops for his Dacian wars .