What caused the fall of the Roman Empire?

defeat by Greece in the Pyrrhic War

lack of cultural cohesion

land region was too large to defend

peasant rebellion

Pyrrhus was the son of Aeacides and Phthia, a Thessalian woman, and a second cousin of Alexander the Great (via Alexander's mother, Olympias). He had two sisters:Deidamia and Troias. In 317 BC, when Pyrrhus was only two [citation needed], his father was dethroned. Pyrrhus' family took refuge with Glaukias of the Taulantians, one of the largest Illyrian tribes.[4] Pyrrhus was raised by Beroea, Glaukias's wife and a Molossian of the Aeacidae dynasty.[2][7]

Glaukias restored Pyrrhus to the throne in 306 BC until the latter was banished again, four years later, by his enemy, Cassander. Thus, he went on to serve as an officer, in the wars of the Diadochi, under his brother-in-law Demetrius Poliorcetes who married Deidamia. In 298 BC, Pyrrhus was taken hostage to Alexandria, under the terms of a peace treaty made between Demetrius and Ptolemy I Soter. There, he married Ptolemy I's stepdaughter Antigone (a daughter of Berenice I of Egypt from her first husband Philip--respectively, Ptolemy I's wife and a Macedonian noble) and restored his kingdom in Epirus in 297 BC with financial and military aid from Ptolemy I. Pyrrhus had his co-ruler Neoptolemus II of Epirus murdered. In 295 BC, Pyrrhus transferred the capital of his kingdom to Ambrakia (modern Arta). Next, he went to war against his former ally and brother-in-law Demetrius and in 292 BC he invaded Thessaly while Demetrius was besieging Thebes but was repulsed. By 286 BC, Pyrrhus had taken control over the kingdom of Macedon, but was driven out of Macedon by Lysimachus in 284 BC.