World's history (part 6): Declines and falls[edit] The empires faced common problems associated with maintaining huge armies and supporting a central bureaucracy. These costs fell most heavily on the peasantry, while land-owning magnatesincreasingly evaded centralised control and its costs.Barbarianpressure on the frontiers hastened internal dissolution. China'sHan Empirefell intocivil warin 220 CE, while itsRomancounterpart became increasingly decentralized and divided about the same time. The great empires of Eurasia were all located on temperate coastal plains. From the Central Asiansteppes, horse-based nomads (Mongols, Turks) dominated a large part of the continent. The development of thestirrup, and the breeding of horses strong enough to carry a fully armed archer, made the nomads a constant threat to the more settled civilizations. The gradual break-up of theRoman Empire,[68][69]spanning several centuries after the 2nd century CE, coincided with the spread of Christianitywestward from the Middle East. The Western Roman Empire fell[70]under the domination ofGermanic tribesin the 5th century, and these politiesgradually developed into a number of warring states, all associated in one way or another with theRoman Catholic Church . The remaining part of the Roman Empire, in the eastern Mediterranean, would henceforth be theByzantine Empire.[71] Centuries later, a limited unity would be restored towestern Europethrough the establishment of theHoly Roman Empire[72]in 962, comprising a number of states in what is now Germany,Austria,Switzerland,Czechia,Belgium,Italy, and parts ofFrance. In China,dynastieswould similarly rise and fall.[73][74]After the fall of theEastern Han Dynasty[75]and the demise of theThree Kingdoms, nomadictribes from the north began to invade in the 4th century, eventually conquering areas of Northern China and setting up many small kingdoms. Postclassical Era [edit] Main article:Postclassical Era The Postclassical Era is named for the more Eurocentric era of"Classical Antiquity,"but"the Postclassical Era"refers to a more global outline. The era is commonly dated from the fall of the Western Roman Empirein the 5th century. The Western Roman Empire fragmented into numerous separate kingdoms, many of which would be later confederated under the Holy Roman Empire. The Eastern Roman, or Byzantine, Empiresurvived until late in the Middle Ages. The Postclassical period also corresponds to theIslamic conquests,[76] subsequentIslamic golden age,[77][78]and commencement and expansion of theArab slave trade, followed by theMongol invasionsin the Middle East and Central Asia. South Asiasaw a series ofmiddle kingdoms of India, followed by the establishment ofIslamic empires in India . In western Africa, theMali Empireand theSonghai Empiredeveloped. On the southeast coast of Africa, Arabic ports were established where gold,spices, and other commodities were traded. This allowed Africa to join theSoutheast Asiatrading system, bringing it contact with Asia; this, along with Muslim culture, resulted in the Swahili culture. TheChinese Empireexperienced the successive Sui,Tang,Song,Yuan, and the beginning of theMingDynasty. Middle Eastern trade routes along the Indian Ocean, and the Silk Roadthrough the Gobi Desert, provided limited economic and cultural contact between Asian and European civilizations. During this same period, civilizations in the Americas, such as the Inca,Maya, andAztec, reached their height. All would be seriously compromised by contact with European colonistsat the beginning of theModern period.