'The Decline'
Chronology

193-194 Second crisis of the Empire: second year of four emperors, Pertinax, Clodius Albinus, Pescennius Niger, Septimius Severus

193-211 Septimius Severus emperor, initiating Severan dynasty

194 Severus recognizes Albinus as Caesar but marches against Pescennius. Defeat and death of Pescennius. His followers hold out for two years in Byzantium.

195-196 Parthian campaign

197 Contest of Severus and Albinus. Death of Albinus at Battle of Lugdunum. Severus sole emperor

198 Severus organizes Praetorian Guard under his own command

199 The province of Mesopotamia is brought back into the Empire

199-200 Septimius Severus in Egypt

204 Secular Games (Ludi saeculares) celebrated throughout the Empire

206-207 Septimius Severus in Africa

208-211 Septimius Severus heads campaign in Britain and dies there

211-217 Caracalla emperor

212 The Constitutio Antoniniana, issued by Caracalla, confers citizenship on all free men in the Empire

216 War again breaks out in Parthia

217-218 Macrinus and his ten-year-old son Diadumenianus co-emperors after murder of Caracalla

218-222 Elagabalus emperor, reestablishes Severan rule

222-235 Alexander Severus emperor

224-241 Artaxerxes I reigns over the new Persian empire of the Sassanids (or Sasanians)

230-232 Campaign against the Sassanids

235-238 Gordianus I and Gordianus II assume emperorship of North Africa

238-244 Gordianus III emperor

241-271 Sapor I, King of Persia

242-243 Victorious campaigns against the Persians; battles of Resenae, Carrhae, and Nisibis

244-249 Philippus Arabs emperor and his son co-regent 247-249

248 Celebration of millenium of Rome

248-251 Decius emperor

250 Persecution of Christians

251 Decius and his son Herennius Etruscus fall in battle in Abrittus against Goths

251-153 Treborianus Gallus emperor

253 June-September, Aemilianus emperor

253-260 Valerian and his son Gallienus co-emperors, while Valerian campaigns in the East and Gallienus governs the West of the Empire

253 Persian War flares up again, Antioch lost to Persia

254-262 Revolts of Bagaudae, insurgent peasants, in Gaul and Spain

257-260 Persecution of Christian by Valerian

260 Valerian taken prisoner by Persians at Edesa

260-268 Gallienus sole emperor

260 Gallienus extends tolerance to Christians

260-272 Queen Zenobia of Palmyra seizes large areas of Asia Minor, Syria, and Egypt and sets up an independant empire until defeated and taken prisoner by Aurelian

261-274 Separatist empire set up in Gaul by Postumus (261-268) and Tetricus (270-274)

268-270 Claudius II Gothicus emperor

270-275 Aurelian emperor

276-282 Probus emperor

282-283 Carus emperor

282-285 Carinus at first co-emperor with Carus and then sole emperor

283 Persian campaign of Carus

284-305 Diocletian and Maximian co-emperors

293 Diocletian creates tetrarchy with himself and Maximian as co-Augusti in the East and West, and Galerius and Constantius Chlorus as co-Caesars

297 The Empire is divided administratively into twelve dioceses, each ruled by a vicarius

301 The Edict of Maximum Prices imposed throughout the Empire

303 Diocletian persecutes the Christians

305 Diocletian abdicates and forces Maximian to do likewise. Galerius and Constantius Chlorus co-Augusti

306 Constantine declared co-Augustus after death of his father Constantius Chlorus, but Galerius recognizes the Illyrian Severus in that rank and confers the title of Caesar on Constantine

306 Maxentius, son of Maximian, hailed as legitimate successor by the Praetorian Guard and the city of Rome; heads revolt against Constantine. His father comes out of retirement to profit from the situation, first on one side, then on the other

308 At an imperial conference of Diocletian, Galerius and Maximian at Carnuntum Licinius is declared Augustus of teh West, setting off an armed conflict between all rival contenders

310 Maximius Daia, nephew of Galerius, assumes on his own initiative the title of Augustus

311 An edict of tolerance for Christians issued by Galerius shortly before his death

312 Constantine's victory over Maxentius in battle at the Milvian Bridge puts Rome in his hands

313 Victory of Licinius over Maximinus Daia at the Hellespont is followed by reconciliation of the two victors

313 The co-emperors issue the Edict of Milan ending persecution of Christians

314 Armed conflict breaks out between the co-emperors: truces, claims, counterclaims, and wars follow for ten years with Constantine increasingly victorious

324 Constantine sole emperor after final defeat, abdication, and execution of Licinius

325 The Council of Nicaea formulates Nicene Creed and makes Christianity the religion of the Empire

326 Constantine chooses Byzantium as the new capital of the Empire and renames it Constantinopolis

337 May 22, death of Constantine the Great