What are some weakening frontiers of Rome?

Some weakening frontiers of Rome included the Rhine and Danube rivers, which faced increasing pressure from Germanic tribes and other groups. Additionally, the eastern frontier became vulnerable due to the rise of the Sassanian Empire, which engaged in frequent conflicts with Rome. Economic decline and internal strife further strained military resources, making it difficult to maintain and defend these borders effectively. This combination of external threats and internal instability contributed to the gradual decline of Roman control over its frontiers.