Final answer:
Octavian, later known as Augustus, is a historical figure who might have vowed not to sheath his sword until peace is restored or his enemies are defeated.
Step-by-step explanation:
The student is likely asking about a historical figure, possibly Octavian who is also known as Augustus, the first Emperor of Rome. Without a specific part of history or quote mentioned in the question, it's challenging to provide an exact answer. However, a phrase that may fit into the blank, given Octavian's historical context, could be 'until peace is restored' or 'until his enemies are defeated,' both of which reflect his vows during various military campaigns and civil strife he navigated through his rise to power. Octavian, after defeating Mark Antony and Cleopatra, worked to secure his rule and bring about the Pax Romana, a period of relative peace and stability across the Roman Empire.