Drusus had been sent in 13 BCE to govern Gaul to quell riots caused by the actions of a previous administrator.

While he was present, a tribe of Germans had entered Gaul and proceeded to attack Roman settlements.

Drusus had mobilized his legions and beat the invaders back across the Rhine, then marched into Germany to defeat a superior force of Sicambri at the Lippe River the following year.

Penetrating deep into German territory, he travels as far as the North Sea and places a yearly tribute on the Frisii.

The Romans thus extend their empire north as far as the Rhine River in the present Netherlands, long occupied by such Germanic tribes as the Batavi and Frisii.

The victorious Drusus, in a show of Roman might, parades his legions back and forth between the Elbe and the Rhine.

As a reward, Drusus is made praetor urbanus for 11 BCE.

Drusus, who does not have it in him to stay in Rome, sets out in the spring of his term for the German border once more.

He pushes again into the territory of the various German tribes, only stopping at the onset of winter.

Attacked while making his way back to Roman territory, he manages to rout the German force.

His troops proclaim him Imperator and he is granted triumphal ornaments, as well as the office of proconsul for the following year.

The Chatti join with the Sicambri in 10 BCE and attack Drusus' camp, but are easily defeated.

Drusus then goes to meet Augustus and Tiberius in Lugdunum (at which point Claudius was born), and travels with them to Rome.

Nero Claudius Drusus, nephew and stepson of Roman emperor Augustus, is easily elected Consul for 9 BCE, but once more leaves the city before assuming office.

He once again smashes the Chatti, and then begins a campaign against the Marcomanni, but is turned back across the Rhine.

Drusus dies soon after in consequence of a fall from a horse, lingering on for a month after the accident.

His brother Tiberius Claudius Nero, who had been at Ticinum, on the Po River, south of what is now Milan, four hundred miles away, rides day and night to be with his younger brother, arriving just in time to see Drusus die.

Interestingly, soon before his death Drusus had written a letter to Tiberius complaining about the style in which Augustus rules.

Suetonius reports that he had refused to return to Rome just before his death.

Tiberius escorts the body back to Rome, walking in front of it on foot all the way.

Drusus' ashes are deposited in the Mausoleum of Augustus.

He remains extremely popular with the legionaries, who erect a monument (the Drususstein) in Moguntiacum (modern Mainz) on his behalf.

Remnants of this are still standing.

His family is granted the hereditary honorific "Germanicus", which is given to his eldest son before passing to his youngest.

Augustus will later write a biography of him that does not survive.

Drusus had in about 16 BCE married the younger Antonia, daughter of Mark Antony and Octavia.

Their surviving children are Germanicus, Livilla, and Claudius, who will later become emperor.

The Batavi, a sub-tribe of the Germanic Chatti tribal group who had rendered valuable aid under the early emperors, had been well treated in order to attach them to the cause of Rome.

They are exempt from tribute, but are obliged to supply a large number of men for the army.

Gaius Julius Civilis, a hereditary prince of the Batavi, the prefect of a Batavi cohort, and a veteran of twenty-five years' service, had distinguished himself by service in Britain, where he and the eight Batavi cohorts had played a crucial role in both the Roman invasion in 43 CE and the subsequent subjugation of southern Britain.

Before and during the disturbances that followed the death of Nero, Civilis had been twice imprisoned on a charge of rebellion, and narrowly escaped execution.

Civilis in early 69 had been released by Vitellius, when the latter, having launched his mutiny against Otho, was in urgent need of the Batavi's military support.

The Batavi regiments, having duly helped Vitellius overthrow Otho at the Battle of Bedriacum, were then ordered to return home, but at this point came the mutiny of Vespasian, commander of forces in Syria.

Vitellius' general in Germania Inferior, ordered to raise more troops, squanders the goodwill of the Batavi by attempting to conscript more Batavi than the maximum stipulated in their treaty.

The brutality and corruption of the Roman recruiting centurions bring already deep discontent in the Batavi homeland to the boil.

Civilis, commanding the Batavian auxiliary troops allocated in the summer of 69 to the Rhine legions, takes up arms under the pretense of siding with Vespasian and induces the inhabitants of his native country to rebel.

The Batavi are immediately joined by several neighboring German tribes, the most important of whom are the Frisii.

Vespasian, who is fighting Vitellius for the imperial throne, salutes the rebellion that keeps his enemy from calling the Rhine legions to Italy.

The Batavi are promised independence and Civilis is on his way to becoming king, but, for unknown reasons, this is not enough for the Batavi.

Civilis chooses to pursue vengeance and swears to destroy the two Roman legions.

The timing is well chosen: with the civil war of the Year of the Four Emperors at its peak, it will take some time before Rome can produce an effective counterattack.

Moreover, the eight Batavian auxiliary units of Vitellius' army are on their way home and can be easily persuaded to join the rebellion for an independent Batavia.

This is an important reinforcement.

Apart from being veteran troops, their numbers are greater than the combined Roman troops stationed in Moguntiacum (Mainz) and …

Marcus Ulpius Traianus was born on September 18, 53, in the Roman province of Hispania Baetica (in what is now Andalusia in modern Spain), a province that was thoroughly Romanized and called southern Hispania, in the city of Italica (now in the outskirts of Seville), where the Italian families were paramount.

He is the son of Marcia and Marcus Ulpius Traianus, a prominent senator and general from the gens Ulpia.

Trajan himself is just one of many well-known Ulpii in a line that will continue long after his own death.

His elder sister is Ulpia Marciana and his niece was Salonina Matidia.

The patria of the Ulpii is Italica, in Spanish Baetica, where their ancestors late in the third century BCE had settled.

He had risen as a young man through the ranks of the Roman army, serving in some of the most contentious parts of the Empire's frontier.

Trajan's father was in 76–77 Governor of Syria (Legatus pro praetore Syriae), where Trajan himself had remained as Tribunus legionis.

The governor of Germania Superior, Lucius Antonius Saturninus, and his two legions at Mainz, Legio XIV Gemina and Legio XXI Rapax, on January 1, 89,  revolt against the Empire with the aid of the Chatti.

The precise cause for the rebellion is uncertain, although it appears to have been planned well in advance.

The Senatorial officers may have disapproved of Domitian's military strategies, such as his decision to fortify the German frontier rather than attack, as well as his recent retreat from Britain, and finally the disgraceful policy of appeasement towards Decebalus.

The uprising is in any case strictly confined to Saturninus' province, and quickly detected once the rumor spreads across the neighboring provinces.

The governor of Germania Inferior, Lappius Maximus, moves to the region at once, assisted by the procurator of Rhaetia, Titus Flavius Norbanus.

Trajan is summoned from Spain, while Domitian himself comes from Rome with the Praetorian Guard.

By a stroke of luck, a thaw prevents the Chatti from crossing the Rhine and coming to Saturninus' aid.

The rebellion is crushed within twenty-four days and its leaders at Mainz savagely punished.

Trajan afterwards burns Saturninus' letters in an attempt to avoid implicating others.

Domitian has numerous others executed with Saturninus, however, displaying their heads on the rostra at Rome.

The Legio XXI is sent to the front in Pannonia, and Domitian passes a law prohibiting two legions from sharing the same camp.

…the capital of the province of Germania Superior, Moguntiacum (present-day Mainz), which serves as base of two (at times three) Roman legions.

Didius Julianus, the commander of the Rhine frontier and future Roman emperor, repels another invasion of the Chatti and the Hermunduri in 173.

He had held in succession the offices of quaestor and aedile, and around 162, had been named as Praetor.

Nominated to the command of the Legio XXII Primigenia in Mogontiacum (now Mainz), he had in 170 become praefectus of Gallia Belgica and will serve for five years.

As a reward for his skill and gallantry in repressing an insurrection among the Chauci, he is raised in 175 to the consulship, along with Pertinax.

Alexander Severus is called to face German invaders in Gaul, who in 234 have breached the Rhine frontier in several places, destroying forts and overrunning the countryside.

Alexander musters his forces, bringing legions from the eastern provinces, and crosses the Rhine into Germany on a pontoon bridge.

Initially on the advice of his mother, he attempts to buy the German tribes off, so as to gain time.

Whether this is a wise policy or not, it causes the Roman legionaries to look down on their emperor as one who is prepared to commit unsoldierly conduct.

Herodian says "in their opinion Alexander showed no honorable intention to pursue the war and preferred a life of ease, when he should have marched out to punish the Germans for their previous insolence". (Herodian, 6:7:10)

The circumstance on the German frontier have driven the army to look for a new leader.

They choose Gaius Iulius Verus Maximinus, who is most likely of Thraco-Roman origin (believed so by Herodian in his writings).

According to the notoriously unreliable Augustan History (Historia Augusta), he was born in Thrace or Moesia to a Gothic father and an Alanic mother, an Iranian people of the Scythian-Sarmatian branch; this supposed parentage is however highly unlikely, as the presence of the Goths in the Danubian area is first attested after the beginning of the Crisis of the Third Century.

British historian Ronald Syme, writing that "the word 'Gothia' should have sufficed for condemnation" of the passage in the Augustan History, felt that the burden of evidence from Herodian, George Syncellus (an eighth century chronicler) and elsewhere pointed to Maximinus having been born in Moesia.

The references to his "Gothic" ancestry might refer to a Thracian Getae origin (the two populations were often confused by later writers, most notably by Jordanes in his Getica), as suggested by the paragraphs describing how "he was singularly beloved by the Getae, moreover, as if he were one of themselves" and how he spoke "almost pure Thracian".

His background is, in any case, that of a provincial of low birth, and is seen by the Senate as a barbarian, not even a true Roman, despite Caracalla’s edict granting citizenship to all freeborn inhabitants of the Empire.

Maximinus is similar in many ways to the later Thraco-Roman Roman emperors of the third to fifth century (Licinius, Galerius, Aureolus, Leo the Thracian, etc.), who elevate themselves, via a military career, from the condition of a common soldier in one of the Roman legions to the foremost positions of political power.

He had joined the army during the reign of Septimius Severus, but had not risen to a powerful position until promoted by Alexander Severus.

Maximinus had been given command of Legio IV Italica, composed of recruits from Pannonia, who are angered by Alexander's payments to the Alemanni and his avoidance of war.

The troops, among whom include the Legio XXII Primigenia, elect the stern Maximinus on either March 18 or March 19, 235, killing young Alexander and his mother at Moguntiacum (modern Mainz).

These assassinations secure the throne for Maximinus.

The Praetorian Guard acclaims him emperor, and their choice is grudgingly confirmed by the Senate, who are displeased to have a peasant as emperor.

Maximinus hates the nobility and is ruthless towards those he suspected of plotting against him.

He begins by eliminating the close advisors of Alexander.

His suspicions may have been justified; two plots against Maximinus are foiled.

The first is during a campaign across the Rhine, during which a group of officers, supported by influential senators, plot the destruction of a bridge across the river, then leave Maximinus stranded on the other side.

Afterward they plan to elect senator Magnus emperor; the plot is discovered, however, and the conspirators executed.

The second plot involves Mesopotamian archers, loyal to Alexander, who had planned to elevate Quartinus, but their leader Macedo changes sides and murders Quartinus instead, although this is not enough to save his own life.

The accession of Maximinus is commonly seen as the beginning of the Crisis of the Third Century (also known as the "Military Anarchy" or the "Imperial Crisis"), the commonly applied name for the crumbling and near collapse of the Roman Empire between 235 and 284 caused by three simultaneous crises: external invasion, internal civil war, and economic collapse.