The crisis of the 3rd Century is known by modern historians
of the period from 235 to 284/85 AD in the Roman Empire.
During this time, when the leadership of the Empire was under the so-called soldier-Emperors, there occurred a series of internal and external crises. The period began at the end of the Severan dynasty, who had proved themselves as a stabilizing factor for the Empire.
armies as well as the new Persian Sassanid Empire threatened the Roman Empire, which had to fend off invasions by in the north and east. Numerous usurpations,
the secession of imperial territories ( The Gallic Empire,
and the kingdom of Palmyra)
and regional economic problems constitute additional burden on the empire during the height of the crisis in 260 . There were several administrative and military reforms embarked during this era to bring the empire back to stability. This final phase of the Principate
ended with the reign of Diocletian
(284/85), which is associated usually the beginning of the Late Antiquity.
The Roman history of the 3rd. Century has lately become a subject of lively academic discussion. Some researchers follow the traditional approach and assume that there was a complete collapse and a systemic crisis of the empire came to touching on all areas of life. Others are much more cautious and argue that represent the various crises especially for the years around 260 out of the question to see the period but rather as a transition phase of the ancient world through to late antiquity, where there had been a promising approach to tackle the "crisis", also had several provinces of the empire during this period even seen a real boom in prosperity. Some researchers doubt whether even in principle, the applicability of the term "crisis" on the condition of the third century.
· 1 History of the “ Crisis of the third century"
· 2 Timeline
· 3 characteristics of the epoch
· 4 Sources
· 5 Research History
· 6 Literature
· 7 comments
History of the "Crisis of the third century"
From Maximinus "Thrax" to Valerian
The first soldier Emperor Maximinus and the Six Emperors
After the Roman Empire
after the turmoil of the second four emperors
(193) during the reign of Septimius Severus
was stabilized again, slipped away from the later Severern
more in control. 
The army, spoiled by high donative,
for the Emperor was always difficult to control. The young, inexperienced and rather weak emperor Severus Alexander
was murdered in 235 in Mainz finally by rebelling forces. In its place, the officer Maximinus
was proclaimed the new emperor. 
Several details regarding Maximinus are unclear, since the sources are biased. He[3 He]
was obviously not a senator, but an equestrian
, as only one Emperor was a senator(Macrinus). He also came from a family that probably had only been relatively recently been granted the Roman citizenship,
although his wife apparently belonged to the nobility. 
His relationship with the Senate
was bad because he renounced to move to Rome and to the institution more to show a superficial respect. Although the Senate was virtually powerless in the imperial age, he still enjoyed a high symbolic value. Even in the army, there was apparently some concern in part because the sources report of rebellion at Mogontiacum
and by stationed troops in the east, although both rebellion (even if they do occur historically) failed. Maximinus was able to secure its power only gradually and awarded a monetary gifts to the soldiers as well as the urban population of Rome. In 235/36 , he led several successful campaigns against Germans
on the Rhine . 
Given this context , we can classify the recent battlefield find at Kalefeld in Lower Saxony as the location of the battle. ( This sentence needs to be re-looked)
The Senate attitude towards Maximinus, whose relationship with many senators did not seem too at ease in the subsequent period, resulted in a revolt in the province of Africa
in the year 238.
Apparently Maximinus was forced to increase the tax burden continues to pay the legions, which resulted in the unrest of the provinces. The Senate moved against the Emperor, and proclaimed the usurper proclaimed Gordian I
Emperor, who had good contacts in Rome and murdered Maximinus' local supporters with the help of the Praetorian and the Urban prefect. (Possible translation error). Also, about half of the provinces defected from the emperor. Gordian appointed his son of the same name
as co-emperor, but he was defeated in the spring of 238 by the loyal troops and was killed, and shortly thereafter, the desperate Gordian I committed suicide. The Senate, which had already been expected with the sanctions on the rise Maximinus placed, then appointed the prestigious Senators Pupienus
as the two "Senate Emperor" – which is an unusual event. However, there was unrest in Rome, with the public pushing for an emperor who was related to the Gordians. Of necessity they rose to the very young Gordian III.,
The grandson of Gordian I, was named Caesar,
while Pupienus Balbinus govern the Empire. 
Pupienus now marched against Maximinus, was stuck at the siege of Aquileia,
and was finally murdered by disgruntled soldiers, together with his son. But even the death of Maximinus did not end the conflict, due to the disputes between Pupienus and Balbinus. The Praetorian Guard,
an important political force in Rome, also threatened the authority of the new government. The guard was apparently does not agree with the Senate’s choice emperors, and perhaps also feared being replaced by a new Guard unit. Hence in 238, the praetorian launched a successful attack on Pupienus Balbinus and, thereafter, they raised Gordian III. as the new emperor (Augustus).
Rome on the defensive: The first attacks of the Scythians and the rise of Sassanid Empire
Even after the end of the turmoil of the Six Emperors
238 stabilized the situation only temporarily: The economic situation was tense because of the high spending on the war against Maximinus added, was the threat from the outside. On the Rhine,
above all, the Alemanni
exerted a pressure, while on the Danube,
had appeared and there were responsible for unrest. While these areas were at risk for a long time, basically the situation was not so new, but the intensity of attacks increased evidently. There were especially now more of tribes) (gentes
as the Alamanni and Franks,
whose considerable clout and their migration
was probably driven by the conflict with Rome. 
In 238, the so-called "los Gotensturm" broke out, and the Goths began their first attack on Roman territory and captured the town, located south of the Danube Histros while Carpi
to the province of Moesia
The history of the struggles against these Germanic invaders from the "classically" oriented Greek authors in the use of traditional ethnography
known as Skythai
described the historian Dexippos
in his (fragmentary) work Skythika.
For Dexippos, the year 238 marks the beginning of the "Scythian war." 
to 248. While the Goths again behaved calmly, the carpi continued their attacks.
The defensive struggles, the Rome since the 30s of the 3rd Century had to pass on the Danube, but were not comparable to any other threat to the empire as threats arose almost simultaneously in the east. There, the new Persian Sassanid Empire represented a far greater threat to Rome than that the- at least initially - sporadic incursions of Germanic tribes.  The Sassanid which had removed the more loosely organized realm of the Parthians in 226 and put in the place of a more centralized state , and possess a much stronger army, especially in the form of armoured cavalry. The Sāsānidenreich, which could look back on an ancient cultural heritage of 400 years), the great rival of Rome in the East to be (for the relevant wars, see Roman-Persian Wars. The Persian King Ardashir I, who wanted by military successes are probably also prove its legitimacy, had for the first time since the era of Alexander Severus advanced into Roman territory, and probably in 236, the strategically important cities of Nisibis and Carrhae fell to the Persians. 
Gordian III apparently tried to maintain a good relationship with the Senate and to the goodwill of the city of Rome population. [13 He] In 241, Timesitheus rose to the position of Praetorian Prefect. He dominated from then on the business of government, and Gordian married his daughter in the same year. Externally, the eastern boundary of Rome remained a focal point: the Sassanians succeeded 240/41, conquered the important city of Hatra too, capital of the Kingdom.  Whether the Sassanian assumed real, as if by western sources,  claims to territories of the old Achaemenes, is questionable and highly controversial. More detailed knowledge of ancient history are not an absolute requirement for the Sassanian. It therefore could also be a Roman interpretation.  The destruction of the Kingdom of Hatra, which had served as an important buffer state in the Roman-Persian border zon, was the reason for the outbreak of new hostilities between Rome and Persia, with much symbols were connected: Gordian left the doors of the Janus temple open in Rome, to underline that Rome was at war. He also asked for the assistance of the goddess Athena Promachus who have assisted the Greeks in the Persian wars, by a cult in Rome for the goddess identified with Athena Minerva donated. Finally, he went Timesitheus of which 243 to the east of the Empire. After initial successes, during which, however, Timesitheus died, and after a heavy defeat suffered by the Romans in the Battle of Mesiche (probably in February) 244 under the Persians by their new king Shapur I, either as a result of fighting or because of an intrigue of the new Praetorian Prefect Philip Arabs, Gordian was killed. 
Philip, who was a sheikh of Arab origin, succeeded Gordian. One of his first actions was to make peace with Persia, apparently bought with large cash payments.  Philip was very concerned about the legitimacy of his rule and tried to maintain a good relationship the Senate. The deceased did he bring to the Gordian divus, and he established this as pointedly to Severan tradition. Nevertheless, there was during his reign to several rebellion, while some were suppressed relatively quickly, others prevailed ( The last until 249) . In 248, Philip committed with great effort, the 1000-year anniversary of Rome, had not modified propaganda value. Presumably, in this context Asinius Quadratus prepared a 1000-year history of Rome, which is (but do not get to a few fragments). The external situation remained strained, but still manageable; in 245/46 Philip successfully led war against the carpi in the Danube region, and finally ensured peace in that area. The Danube frontier continued to be one of the most vulnerable border regions, because according to Karpen, the Goths, and the Scythians once again invaded Thrace in 249.  They also laid siege to the city Marcianopolis, but eventually withdrew. [ 20] In 249, there was the usurpation of an army commander: Decius, who had successfully taken action against Germanic tribes along the Danube, had himself proclaimed emperor by his troops. Philip fell shortly afterwards in the fight against Decius.
Decius, grew to be the Emperor's programmatic surname Traianus,
came from the senatorial elite. 
Apparently, he was quite a traditionalist bent, for he tried hard to maintain the traditional gods and cults were rigorously before against Christians,
and a 250 from him Victims should be enacted edict forcing all inhabitants of imperial sacrifices to the gods. To Decius, it probably was primarily a demonstration of loyalty and it should have been clear that the Christian was presented the choice to renounce their faith or die. There were arrests and killings, and it became virtually the first empire-Christian persecution.
A religion such as Christianity, which stood in contrast to the traditional gods, cults, is seen as a provocation to the traditionalists Decius, as the gods was seen as protectors of Rome, an important function in the Roman state. The Christians were initially taken completely by surprise While a large number of them renounced their faith, others suffered more death, including the eminent scholar Origen. Christianity has taken decisive but hardly, if only because of the brevity of the action: Decius looked under the situation in the Danube region soon forced to take action against these Goths. In 251, he undertook a campaign against them, but was defeated by the King Cniva
and together with his son Herennius Etruscus
, he was killed.
The successor of Decius was Trebonianus Gallus,
one of the few imperial soldiers who came from Italy. Trebonianus Gallus was faced with another problem: A disease that had probably originated in what is now Ethiopia,
which had spread to North Africa and seems to be spreading farther north. In the East, the Sassanian continued their attacks on the Eastern Roman provinces; Persian troops reached Roman-occupied Mesopotamia and Armenia in 252. Meanwhile in the north, Alamanni appear to have become active. Trebonianus Gallus no longer had the time to respond to these threats, because he was killed as a result of the usurpation of the 253 by Aemilianus.
Aemilianus was able to hold only a few weeks in power, before the commander Valerian,
which Trebonianus Gallus had called for help, had arrived was assassinated by his own troops. With the new Emperor Valerian, the situation stabilized, although it is temporarily, but should only do the Empire during his reign, a massive escalation of problems and the actual time of crisis.