What Role Did Emperor Geta And Caracalla Play Militarily?

I like imagining Roman imperial drama like a grim afternoon soap, and Geta and Caracalla are perfect cast. Geta was the younger, less battle-hardened brother — more courtly, less in the field — so he never really commanded the legions. He had the title but not the troops, which in the late Roman world is a fatal weakness.

Caracalla, conversely, was obsessed with military backing. He’d seen how decisive soldiers were during his father’s campaigns and he doubled down: generous donatives, public largesse, and clear signals that the army’s loyalty was worth buying. He used those ties to liquidate rival power — Geta was killed in the context of this struggle — and then pursued campaigns and policies that kept the army central to ruling the empire. The practical takeaway is simple and harsh: in that era the sword, not the senate, decided who wore the crown, and Caracalla understood — and exploited — that truth in ways Geta never did.

I read a lot of late-Roman history for fun, and when I think about Geta versus Caracalla I see two very different relationships with the army. Geta was nominally co-Augustus but never really built a military identity. He stayed more in Rome, relying on formal titles and senatorial prestige. That’s important: by the third century the emperor’s legitimacy depended less on paperwork and more on who could command the loyalty of the legions and the Praetorians. Geta simply didn’t have that muscle.

Caracalla’s approach was visceral and pragmatic. He’d been around the front with his father and learned policies that appealed to soldiers — bigger pay, visible favors, and tough, public postures. After their father’s death the competition for control became a matter of which brother could control the armed men. Caracalla used the troops decisively, both to remove Geta and to keep provincial commanders in line. He also implemented the Constitutio Antoniniana, which widened citizenship and indirectly affected recruitment and taxation across the empire — more citizens meant a broader legal claim on imperial authority and fiscal resources to fund the military. Militarily, then, Geta was sidelined and ultimately eliminated; Caracalla, for all his cruelty, was the one who shaped army loyalty and used military force as the engine of political power, with consequences that echoed through the rest of the Severan period.

I’ve always been fascinated by sibling rivalries in history, and the story of Geta and Caracalla is one of the more brutal ones. In military terms, Geta was mostly the sidelined brother. He carried the title of co-emperor after their father’s death, but he never secured the kind of loyal army base that really mattered in late Roman politics. He wasn’t the son who’d grown up shadowing the legions or dispensing pay and honors to soldiers; instead, most contemporary sources paint him as backed by the senate and civilian circles in Rome, not by hardened troops at the front.

Caracalla, on the other hand, is the classic ‘soldier-emperor’ archetype. He had real military experience with his father on campaign and knew how to keep troops loyal: higher pay, generous donatives, and the kind of public gestures — think big bath complexes and lavish building projects funded by military spoils — that signaled where patronage flowed. He moved decisively to secure the army’s support after his father died, and that solidarity let him eliminate Geta in a violent purge. The murder itself was carried out with soldiers present, which shows how central the military was to settling imperial disputes.

Beyond that power grab, Caracalla’s reign left long military footprints: he raised soldiers’ pay and extended citizenship widely with the Constitutio Antoniniana, which had fiscal and recruitment implications for the legions. Geta’s role, militarily speaking, was marginal and brief — more of a political rival than a commander — while Caracalla actively used and reshaped military loyalty to hold the empire together, however ruthlessly, and that’s why his name keeps popping up in the sources I read like 'Cassius Dio' and 'Herodian'. I still get chills thinking of how personal ambition could be decided by who the soldiers cheered for that day.