towards Italy, crossing the Alps with his war elephants. After 15 years of fighting, the Roman republican army beat him and then sent troops against Carthage itself, defeating it in 202. The Second Punic War alone cost Rome 100,000 casualties. In 146, Carthage was finally destroyed completely at the end of the Third Punic War. Rome suffered from various internal disturbances and instabilities. In 133, Tiberius Gracchus was killed alongside hundreds of supporters after trying to redistribute public land to the poor under the lex agraria. The Social War (91-88) was caused by neighbouring cities trying to secure themselves the benefits of Roman citizenship. In 82, general Sulla captured power violently, ending the Roman Republic and becoming a dictator. Following his death new power struggles emerged, and in Caesar's Civil War (49-46), Julius Caesar and Pompey fought over the empire, with the former winning. After the assassination of Julius Caesar in 44, a second civil war broke out between his potential heirs, Mark Antony and Augustus, the latter gaining the new title of Roman emperor. This then led to the Pax Romana, a long period of peace in the Roman Empire. The quarrels between the Ptolemaic Kingdom, the Seleucid Empire, the Parthian Empire and the Kingdom of Pontus in the Near East allowed the Romans to expand up to the Euphrates. During Augustus' reign the Rhine, Danube, and the Sahara became the other borders of the empire. The population reached about 60 million. Political instability in Rome grew. Emperor Caligula (37-41) was murdered by the Praetorian Guard to replace him with Claudius (41-53), while his successor Nero (54-68) was rumored to have burned Rome down. The average reign from his death to Philip the Arab (244-249) was six years. Nevertheless, external expansion continued, with Trajan (98-117) invading Dacia, Parthia and Arabia. Its only formidable enemy was the Parthian Empire. Migrating peoples started exerting pressure on the borders of the empire in the Migration Period. The drying climate of Central Asia forced the Huns to move, and in 370 they crossed Don and soon after the Danube, forcing the Goths on the move, which in turn caused other Germanic tribes to overrun Roman borders. In 293, Diocletian (284-305) appointed three rulers for different parts of the empire. It was formally divided in 395 by Theodosius I (379-395) into the Western Roman and Byzantine Empires. In 406 the northern border of the