Who negotiated an agreement for peace with the barbarians?

The Roman general and statesman Marcus Licinius Crassus is known for negotiating agreements with various barbarian tribes during the late Roman Republic. His most notable engagement was with the Parthians and other groups, where he sought to secure peace and stability along the Roman borders. However, it's important to note that many Roman leaders, including Julius Caesar and Augustus, also engaged in negotiations and military actions with barbarian tribes to maintain peace and expand the empire.