Tacitus recounts another peculiar incident during this period, which undoubtedly served as an unwelcome distraction for Agricola. It appears that the Cohors Primae Ubiorum from Germany decided to revolt, resulting in the death of a centurion and the instructors tasked with their basic training. “They commandeered three small warships (liburnicae), forcibly taking the helmsmen aboard,” writes Tacitus (Agr. 28.1), before delving into the somewhat comical details of their clumsy voyage, culminating in the statement that “thus, they sailed around Britain” (Agr. 28.3).

This tale of “bold and extraordinary wrongdoing” (Tac., Agr. 28.1) became so renowned that Cassius Dio included it in his Roman History, later excerpted by Xiphilinus, who mistakenly believed that Britain was only discovered to be an island due to this voyage. However, as we will soon see, Agricola himself organized a maritime reconnaissance to conclude his governorship. Dio’s rendition also demonstrates how minor elements can become distorted in transmission, as he records that “they killed their centurions and a tribune” (66.20.2). Yet, Dio’s addition of a tribune as their commanding officer was likely unnecessary, as it was plausible for a unit in training to be overseen by a legionary centurion. These centurions often assumed positions of authority, designating themselves as curam agens (“acting in charge”) or as the praepositus (literally “one placed in command”) of a unit, while maintaining their rank as centurion.

After expelling the Romans from their ranks, the rebellious Usipi cohort hurried to a nearby port and seized three Liburnian warships, known for their speed and small size.

The ship captains resisted cooperation, forcing the Usipi mutineers to rely on their limited navigational skills. This possibly led to their slow progress and, unintentionally or not, they are said to have sailed around the entire island. During their extended voyage, the mutineers exhausted their initial supplies. Desperate for sustenance, they began attacking British coastal settlements for food and water. However, many of these assaults were repelled by the Britons, leaving the Usipi with scant resources. Driven to extremes, there are reports of them resorting to cannibalism as their ordeal worsened.

Post circumnavigating Britain, the fate of these mutineers grew unclear. Their raiding activities earned them a pirate-like reputation, despite their inadequate seafaring skills. Tacitus ambiguously noted that the Usipi either ran aground or wrecked their ships, likely along the European mainland near the Netherlands. Back in Germania, they found no friendly reception, likely due to their piratical notoriety. Tacitus recounts, “Having lost their ships through poor seamanship, they were taken for pirates and cut off first by the Suebi and then by the Frisii. Some were enslaved and traded until they reached our side of the Rhine, where their extraordinary journey became well-known” (Agricola, section 28).

This narrative also sheds light on an intriguing aspect of Roman military conscription. In addition to recruiting from provinces with ample manpower reserves such as Spain, Gaul, and Thrace, auxiliary units were intentionally sourced from Rome’s more martial neighbours. The Usipi, also known as the Usipetes elsewhere, seemed like an ideal candidate for recruitment. Their territory stretched along the river Lahn in Germany, which feeds into the Rhine near Koblenz. During the turmoil of AD 69, when Germanic warbands crossed over to support the Batavian revolt and besieged the fortress at Mainz, the Usipi were inevitably drawn into the conflict by their larger and more turbulent eastern neighbours, the Chatti (Tac., Hist. 4.37).

Following these events, the warriors from other tribes in the vicinity, such as the Baetasii, Cugerni, and Frisiavones, were organized into individual cohorts and relocated far from their homelands. It would have been expected for the Usipi to undergo a similar fate. The only surprising aspect is the delay in their conscription, which occurred nearly a generation later.