As the 3rd century dawned, the Roman Empire was at its peak. In the Mediterranean, peace had reigned for over two centuries, as piracy had been wiped out and no outside naval threats occurred. As a result, complacency had set in: naval tactics and technology were neglected, and the Roman naval system had become moribund. After 230 however and for fifty years, the situation changed dramatically. The so-called "Crisis of the Third Century" ushered a period of internal turmoil, and the same period saw a renewed series of seaborne assaults, which the imperial fleets proved unable to stem. In the West, Picts and Irish ships raided Britain, while the Saxons raided the North Sea, forcing the Romans to abandon Frisia. In the East, the Goths and other tribes from modern Ukraine raided in great numbers over the Black Sea. These invasions began during the rule of Trebonianus Gallus, when for the first time Germanic tribes built up their own powerful fleet in the Black Sea. Via two surprise attacks (256) on Roman naval bases in the Caucasus and near the Danube, numerous ships fell into the hands of the Germans, whereupon the raids were extended as far as the Aegean Sea; Byzantium, Athens, Sparta and other towns were plundered and the responsible provincial fleets were heavily debilitated. It was not until the attackers made a tactical error, that their onrush could be stopped.