The Parthian Empire grew out of the ashes of the old Hellenistic Seleucid Dynasty. Parthia itself was an old province of the Achemenian Dynasty, which collapsed after the conquest of Alexander the Great in 321 BCE. The language spoken by the population resembled Old Persian related to modern Farsi, which is the official language of Iran. Parthia was always a frontier state, situated on the fringes of he Achemenian Empire near modern day Turkmenistan.
A prince named Arasces, was the first Parthian to declare his state independent from the larger Seleucid kingdom. The Seleucid king, Antiouchus IV responded by sending an expedition to quell the rebellion. Although it was partly successful, Antiouchus was not able to fully bring Parthia back into his empire. Parthia was gone for good. In 125 BCE, Mithradates I of Parthia attacked the Seleucids and was able to capture Media, Persis and parts of northern India. Mesopotamia would be added later by another king, Volgases in 83 BCE. Thus the empire reached its full height and began to come in contact with Rome.
The first official diplomatic recognition between the two states came after Sulla captured the last Seleucid province around 80 BCE near modern Syria. The two states remained under cordial terms until the time of the first triumvirate. At that time a power-hungry senator would come to cause one of the worst disasters in Roman history.
The Battle of Carrahe:
The wealthy senator, Crassus was the man credited with crushing the Spartcus rebellion of 321. Afterwards he along with Caesar and Pompey shared power in Rome. Pompey and Julius Caesar both had great military conquests under their belts, Crassus not wanting to be left out decided to attack the only empire that was left: Parthia.
On 53 BCE, Crassus financed a private army and crossed the Euphrates river. His course was a direct and bold path straight to the Parthian capitol in Mesopotamia. Plutarch writes that he had a well-equipped army of 40,000. Somewhere past modern day Harran or Carrahe, Crassus was met with a force of 5,000 Parthian Horsemen. Led by the Parthian nobleman Surren, the Parthian horse-archers harassed the mostly infantry Romans. After a Roman Cavalry charge failed, the situation became desperate. Soon, the great Roman force was surrounded as 1000 heavily armed Parthian Knights cut through the Roman lines. Some of the legionaries where able to retreat back to Carrahe bur Crassus and most of his soldiers all died.
An even greater humiliation was the capture of the legions ceremonial standards and insignia by the Parthians. After that, Rome recognized Parthia as the power in the east and never contemplated its total conquest again.
For the next some 400 years, the provinces of Mesopotamia and Armenia would cease-saw back and forth between the two powers. Parthia would always be able to achieve important victories but never be able to follow up on them. Compared to Rome, it was a more of a confederation of allied states than a centralized kingdom. Its intensely feudalistic nature kept it on the defensive until the state finally imploded from within.
In 226 ADE, following Emperor Severus devastating invasion of Mesopotamia, a revolution broke out in the Parthian Empire. In the semi-independent province of Persis, a young nobleman gave himself the title "King of Kings". Artaxerxes or Ardashir claimed to be a direct descendent of the old Achemenian kings. He pointed at the Arasces lax attitude toward foreign religions and people as sign that they were not "purely" Persian. After commanding the Parthian armies for many years, Aradshir used them to turn on his old king. The last Parthian King Artabanas was defeated and beat to death with a royal scepter. Thus the Sassanid Dynasty was born.
Ardashir took his dynastic name from his grandfather, Sassan and immediately began to rebuild the mighty Persian Empire of 700 years past. His attacks into Roman Mesopotamia were unsuccessful but his descendents carried on the struggle. Slowly and methodically, the Sassanids rebuilt their empire to a more centralized state with all the power held by the King. Around 585 ADE, King Khusrau was able to conquer an empire form Egypt to China. However it had to be given up soon and in 635 Muslim invaders from the south destroyed the Sassanid Dynasty.
Begginning around 270 AD, large bands of Lower Germanic tribes banded together to raid Roman Gaul. They called themselves the bold or the Franks. At about the time of Diocletian, the Franks and other tribes settled permanently in Gaul. Although other Roman leaders did defeat them, they were never able to drive them back out. The Kingdom of the Franks made small gains until 486, when King Clovis conquered all the rival Germanic states and made Franks the most powerful nation in Europe. His descendent, Charlemagne or Charles the Great went even farther and conquered most of Western Europe. It is from the Franks that France got its name and from them their empire that modern Europe was born.
The Vandals where a tribe from eastern Germany. They made their first mark on history during the year 406 when they (along with other tribes) crossed the Rhine and attacked Roman Gaul. After three years of plunder they crossed the Pyrennes, entered Spain and began to distribute the land among themselves. Thriteen years later while under pressure from the Visigoths and while seeking new lands for plunder they entered North Africa. Their clever one-eyed, lame leader Gaiseric organized the 80,000 strong seaboard invasion. North Africa was weakly defended and did not put up much of a fight. After the capture of Carthage, Gaiseric built a fleet and began plundering Roman ships. His pirates even sacked undefended Rome for an incredible 14 days. Gaiseric also hated the Catholic Church, although he was a Christian himself. The Vandals took great care to destroy any churches they found. It is most likely because of later Christian writers that the word vandal has the meaning it does today. Despite their brilliant leader, the Vandals were not able to build a strong kingdom. 50 years after Gaiseric's death, a small Byzantine army landed in North Africa and destroyed every trace of the Vandals.
According to legend, the Goths were said to have originated from Scandinavia. They slowly migrated southward until they reached the area north of the Black Sea. Their leader Odin was said to have governed a city during the time of Pompey the Great. Starting from 235, they started making noticeable raids across the Danube. Around 300, their tribe began to drift in half. Some (the Ostrogoths) stayed to the east while the Visigoths remained just beyond the Danube. In any event both tribes were coming under incredible pressure from the east. The Huns were swarming through from the Asian steppes. After the Ostrogoths were subjugated, the Visigoths fled to Rome in fear. Although they were allowed to enter the empire peacefully, they were badly mistreated. In 378, the Visigoths where able to inflict a devastating defeat on the Romans. Afterwards, under the leadership of Alaric they raided Italy and sacked Rome in 410. Eventually they moved out of Italy and into Spain where they founded the Kingdom of Toulouse. At one point the Visigoths stretched from northern Gaul to the tip of Spain. The Franks forced them out of Gaul 100 years later and their Spanish possessions were lost to Moors in 711.
It is hard to say how much of an influence the Huns truly had in the fall of the Roman Empire. Their powerful leader, Attila has become synomous with the modern term of "barbarian". But the Huns failed to ever establish a kingdom within the old Roman Empire contrary to the other tribes. What they did accomplish was causing the mass migration of the German tribes into the Roman Empire.
Most historians agree that the Huns probably originated in northern China. Whether because of drought or tribal rivalries they began a long trek across the vast Asian continent. Along they way they subjugated any tribes in their path and attacked Persia. Due to their furious nature and skill as horse-archers they easily over powered the European tribes they met. In 445, their huge empire was ruled solely by Attila. Organizing the conquered tribes as allies Attila crossed the Danube and besieged Constaniople. Then he turned westward and attacked Gaul where he was temporarily defeated by a combined Roman-Visigothic force. Not showing any real signs of defeat, he instead turned eastward and destroyed Milan. As he was preparing to attack Constaniople again, Attila suddenly died of a nosebleed. The Hunnic Empire soon collapsed afterward and their conquered tribes left the alliance.
Conceivably, the Romans could have fended off the German barbarians that were attacking the frontiers in the fourth century. Afterall, they were nothing new and the Roman military was predominately made up of barbarian recruits anyway. However, the Huns symbolized a new kind of threat that would have eventually caused the demise of the vast Roman Empire. Indeed other Mongolian tribes such as the Avars, Magyars, Tartars, Bulgars would continue to attack the west. Magyars founded the state of Hungary after pillaging Europe and it was the Turks who finally conquered the Byzantines in 1453.