Marcus Aurelius Antoninus and his adoptive brother and co emperor Lucius Aurelius Verus (Ruled 161AD to 169AD) were Roman emperors from 161AD to 180AD. Historian considered him as last of the Five Good Emperors

He was also the last emperor of the Pax Romana (27 BC to 180 AD), an age of relative peace and stability for the Roman Empire.

Rebuilding Power of Rome

Within a year after becoming the emperor the Tiber overflowed its banks and flooded much of Rome. It drowned many animals and destroyed food which left the city in famine.

Marcus Aurelius and his co-emperor Lucius Aurelius Verus gave the crisis their personal attention. They even went to the extent of providing for the Italian communities out of the Roman granaries.

In 165AD, a plague broke out in Rome and devastated the population of the Roman Empire. The plague caused the deaths of five to ten million people, roughly 10 percent of the population of the empire.

The disease was particularly deadly in the cities and in the Roman army.

In 169AD, the plague even claimed the life of his co-emperor Lucius Aurelius Verus.

He rebuilt the army and economy after these devastating events.

Roman–Parthian War

Soon after Marcus Aurelius became the emperor, the Roman Empire witnessed heavy military conflict against the revitalized Parthian Empire.

Even Kingdom of Armenia broke free from Roman domination and sided with Parthian Empire.

From 161AD to 166AD the Roman army fought a continuous war with Parthian Empire known as Roman–Parthian War of 161–166AD. The war was mainly fought for the control of Armenia and Upper Mesopotamia.

The Roman army not only occupied Armenia but launched invasion of Parthia by invading into Lower Mesopotamia. By 165AD, the Roman Army reached Parthian capital of Ctesiphon. The Roman army looted Ctesiphon and set its royal palace to flame.

At the end of the war upper Euphrates became part of the Roman Empire and Armenian again became the Roman client state.

Marcomannic Wars 

During the early 160s, Germanic tribes attacked and destroyed many border posts of the Roman Empire. It appears to historians that the peoples of central and northern Europe were in turmoil.

Starting in the 160s, due to the pressure from eastern tribes, Germanic tribes simultaneously launched raids along the northern border of the Roman Empire, particularly into Gaul and across the Danube River. Chatti tribe launched the first invasion in the province of Germania Superior in 162AD but roman forces repulsed this invasion.

During that time, as the plague was ravaging the empire, Marcus Aurelius was unable to do anything to stop these raids.

Later the Marcomanni tribe invaded with a far better army. They crossed the Danube in 166AD and together with the Lombards and other Germanic tribes won a decisive victory over a force of 20,000 Roman soldiers near Carnuntum.

This disaster forced Emperor Marcus Aurelius to re-evaluate his priorities. He reorganised his army and led them against these Germanic invasions.

In 172, the Roman Army under Emperor Marcus Aurelius crossed the Danube into Marcomannic territory. There Roman army defeated and subjugated Marcomanni and their allies.

In 173, the Romans campaigned against another rebellious tribe called Quadi. This tribe had broken their treaty with the Romans and assisted the Marcomanni Tribe. The Roman army easily defeated and subdued the Quadi tribe too.

Emperor Marcus Aurelius thought that the power of the Germanic tribe had been broken, and withdrew from Germania.

Few years later in 177 AD, the Quadi tribe rebelled, followed soon by their neighbours, the Marcomanni tribe. Emperor Marcus Aurelius once again headed north, to begin his second Germanic campaign. He arrived at Carnuntum in August 178, and set out to quell the rebellion in a repeat of his first campaign. By 180AD, he was able to break the power of the rebellious Germanic tribe.

Though Emperor Marcus Aurelius defeated the Marcomanni, Quadi, and other Germanic tribe in the Marcomannic Wars, but  in long scheme of things Germanic peoples has just started their campaign for the Roman empire and became bigger threat to roman empire after the death of Marcus Aurelius.

Contribution to the philosophy of Stoicism (philosopher king)

During his lifetime Emperor Marcus Aurelius acquired the reputation of a philosopher king. This title would remain with him even after his death.

Emperor Marcus Aurelius wants to improve his mental state. So, he wrote 12 books to provide himself with guidance and wisdom.

He wrote most of his books during his military campaigns from 170 to 180AD.

Though Marcus Aurelius never intended to publish his books, his admirer published the book after his death.

The book had no official title but his admirer gave the book title called “Meditations” as one of the   strong themes of the book is to maintain focus and work without distraction while maintaining strong ethical principles.

He also advocated Stoic ideas like avoiding indulgence in sensory gratification, which will set a man free from the pains and pleasures of the material world.

Contribution to Law

Due to his good upbringing and education, Marcus Aurelius became proficient in imperial administration by the time he became emperor.

Like many previous emperors, Marcus spent much of his time addressing matters of law such as petitions and hearing disputes. However he took great care in the theory and practice of legislation while giving his decision.

Area where emperor Marcus Aurelius had greatest impact in changing the law of Rome was the manumission of slaves, the guardianship of orphans and minors, and the choice of city councillors