Final answer:
The Visigoths invaded Rome in 410 C.E., and the Vandals followed with another invasion in 455 C.E., both of which contributed to the downfall of the Western Roman Empire.
Step-by-step explanation:
The groups that invaded Rome in 410 C.E. and 455 C.E. were Germanic tribes, specifically the Visigoths in 410 C.E. and the Vandals in 455 C.E. The Visigoths, having migrated from Scandinavia and settled in various parts of the Roman Empire, famously breached the walls of Rome in 410 C.E., leading to a sack that shattered the myth of Rome's impregnability. This was the first time in approximately 700 years that the city had been overrun by non-Romans. Then, later in the fifth century, the Vandals, originally from present-day Poland, traversed various regions, eventually establishing a kingdom in Roman North Africa, and in 455 C.E., they carried out another sack of Rome, further exemplifying the decline of the Western Roman Empire.