This legion was raised from marines of the Mediterranean fleet at Ravenna during the tumultous year of ad69, probably by Vespasian or his supporters, shortly after Legio I Adiutrix was raised by Nero from sailors at Misenum, the latter unit later commandeered by Galba. The word Adiutrix means 'assistant, helper', in other words these legions were raised to supplement the existing legionary strength. Most of the sailors in the Roman fleet originated from amongst the sea-faring peoples of the eastern Mediterranean and had a normal service period of twenty-six years, a year longer than the Auxiliaries, and therefore belonged to a subservient branch in the Roman Military hierarchy. Many sailors would have jumped at the chance being offered, for service in the legions, although tough, was of shorter duration than the auxilia and was much more lucrative, being paid significantly higher salaries.
During the revolt of the German armies under Julius Civilis in 69/70, Legio II Adiutrix formed part of the army of nine legions under the joint command of Quintus Petilius Cerialis and Appius Annius Gallus, sent by the new emperor Vespasian to settle the dispute. The imperial legions involved in this conflict were; II Adiutrix, VIII Augusta, XI Claudia, XIII Gemina and XXI Rapax from Italy (all but the last being part of the victorious army from the second battle of Cremona), together with I Adiutrix, VI Victrix and X Gemina from Spain also XIV Gemina, recently removed from Britain.
Following the revolt of the Brigantes tribe under Venutius in ad71, Legio II Adiutrix was despatched to Britain along with the new governor Petillius Cerialis, recently victorious on the Rhine in Germany. The legion appears to have been used as a reserve force, being stationed at Lindum (Lincoln, Lincolnshire), replacing Legio IX Hispana which Cerialis moved north to construct a new fortress at Eburacum (York, North Yorkshire), closer to the source of the revolt and within the territories of the Brigantes themselves.
The next governor of Britain, Gnaeus Julius Agricola, immediately upon arrival in his new domain, set about reorganising the existing legions in preparation for his planned conquest of the Caledonian tribes in Scotland. He moved Legio II Adiutrix from Lincoln to the mouth of the River Dee on the northern Welsh border, where they were to construct a legionary fortress at Deva (Chester, Cheshire). This energetic governor then defeated the Ordovices tribe in North Wales and conquered the Isle of Mona (Anglesey), all during his first year in office.
It is very likely that the cream of II Adiutrix soldiers were used in the Welsh campaigns of Agricola while their comrades toiled to construct the fortress on the Dee. It is also possible that the first cohort at least, may have accompanied the governor throughout his campaigns in Scotland. This is purely speculation, however, as no documentary or epigraphic evidence has been found that places II Adiutrix in either Wales or Scotland at this time.
The bulk of the legion were again used as a reserve force while the action occurred far to the north of Scotland throughout ad78-86. When Agricola was recalled to Rome by Domitian c.87, Legio II Adiutrix were also removed from Britain, to be replaced at Chester by Legio XX Valeria Victrix which had to be removed from Scotland, abandoning their partly-constructed legionary fortress at Inchtuthil in Tayside.
The recovery of a tombstone of an experienced centurion at Colchester, a colony for retired legionary veterans, cannot be taken as evidence of this legion's presence in Essex at any time, neither can the tombstone of a common legionary soldier found at Bath in Avon, where military officers and men would often retire to 'take the waters'. A couple of tombstones recovered from the environs of the legionary fortress at Lincoln, which had no colonial attributions until the late-first century, is, however, seen as evidence that Legio II Adiutrix was stationed here for some time. The fine tombstone of a cavalry officer in the eques or 'cavalry wing' of Legio II Adiutrix, along with at least ten other inscribed funerary monuments attributed to the Legion at Chester attests to their presence here for a period.
Decebalus caused the tribes in Dacia to rise in revolt against Roman rule in ad85 and the first Dacian campaign of Domitian, under the command of the praetorian prefect, Cornelius Fuscus, ended in disaster in ad86. Following this, Legio II Adiutrix was moved from Britain, together with IV Flavia from Dalmatia and I Adiutrix from Germany to strengthen the Dacian Frontier. These legions were used during the victorious campaign of governor Tettius Julianus in ad88, when Roman victory was secured at Tapae.
II Adiutrix were based at Singidunum (modern Belgrade, capital of Serbia) together with Legio IV Flavia during Trajan's Dacian campaigns c.ad105.
The legion was moved from Singidunum to Aquincum (modern Budapest, capital of Hungary) c.ad106, when parts of the Dacian army were redistributed to allow Trajan to continue with his ill-fated campaign in Parthia. The future emperor Hadrian served as a military tribune in Legio II Adiutrix during these campaigns (vide Aelius Spartianus The Augustan History Hadrian.2).
Between ad171 to 173 Legio II Adiutrix was active in the Dacian campaigns of Marcus Aurelius, during which time they were stationed at Trencin in western Slovakia near the border with the Czech Republic, sixty miles beyond the Danube forming the northernmost Roman garrison in Central Europe.