Legio XV Primigenia Roman vexillum

The Legio XV Primigenia was a relatively late-founding legion, created by Emperor Caligula in 39 AD along with its "twin," the XXII Primigenia, and dedicated to the goddess Fortuna Primigenia, who was particularly revered at court. Initially intended for the major Germanic offensive planned by the princeps, it crossed the Alps in the autumn of 39 to be deployed along the Rhine, in the Germanic area, where it remained for its entire brief existence.

Its main castrum was Castra Vetera, near modern Xanten, a strategic hub for controlling Germanic tribes and river routes.

During the Year of the Four Emperors, the XV Primigenia sided with Vitellius, participating in his campaigns against Galba and then against Otho, confirming the strong political weight of the legions on the Rhenish frontier. Returning to Castra Vetera, it was involved in the Batavian revolt of 69–70, when the Batavians, exploiting the civil chaos, besieged the camp. Despite the dispatch of reinforcements, the XV Primigenia, along with the V Alaudae, was forced to surrender in March 70 and subsequently annihilated, being formally disbanded under Vespasian.