The origins of Marcus Claudius Tacitus are disputed. In fact not much is known about him at all. The ancient literary sources, making him a fabulously rich Italian, appear to be fiction rather than fact.
At the death of Aurelian he was not with the emperor and his army in Thrace, but staying at his house at Baiae in Campania, perhaps having retired from service.
Once Tacitus learnt of his elevation to the throne he left for Rome, to accept the senate's confirmation of position in person.
With Tacitus taking power there was the promise of dynastic rule and the stability which accompanies it. For he had several which might have succeeded him. Tacitus' desire include his family in influential positions also showed, when he made his half-brother, Florian, praetorian prefect.
For all its promise, the reign might have been a very tranquil one, would it not have been for another wave of Germanic invasions. The Franks, the Alemanni, and a tribe called the Longiones (lugii) crashed into Gaul and the Goths and the Heruli once more crossed the Black Sea to wreak havoc on Asia Minor (Turkey).
Tacitus decided the Gothic invasion was the more urgent matter. Also Aurelian's army appeared still to be in Thrace. Accompanied by Florian he led the legions into Asia Minor and defeated the barbarians in battle in spring of AD 276.
There are two versions of events surrounding Tacitus' death at Tyana in Cappadocia shortly after his victory over the barbarians. One version tells of the very same murderers who had just shortly before assassinated his relative, the governor of Syria called Maximinus, then journeyed from Syria to kill Tacitus.