The Silk Road was a network of trade routes between Asia and Europe connecting Chang-an, China with Antioch, Syria and other points. Silk first appeared in Rome in about 1 AD. The Silk Road stopped serving as a shipping route for silk in around 1400. Silk road is a translation from the German Seidenstraße, the term first used by German geographer Ferdinand von Richthofen in the 18th century.
With extremely rare exceptions such as Marco Polo, no one travelled down the entire length of the silk road. Instead traders moved products in a bucket brigade fashion from China to the West.
The heyday of the Silk Road corresponds to that of the Byzantine Empire in its west end, Sasanid Period to Il Khanid Period in the Nile-Oxus section and Three Kingdoms to Yuan Dynasty in the Sinitic zone in its east end. Besides the continental Silk Road, historians also talk of a "Porcelain Route" or "Silk Route" across the Indian Ocean. Columbus wished to create another Silk Route.
The continental Silk Road diverges into North and South routes as it extends from the commercial centers of North China, the North route passing through the Bulgar-Kypchak zone to Eastern Europe and the Crimean Peninsula and from there across the Black Sea, Marmara Sea and the Balkans to Venice; the South Route passing through Turkestan-Khorasan, through Iran into Mesopotamia and Anatolia, and then through Antioch in Southern Anatolia into the Mediterranean Sea or through the Levant into Egypt and North Africa.
The Silk Road is an interesting subject for those who want to observe an early phenomenon of political and cultural integration due to inter-regional trade. In its heyday, the Silk Road sustained an international culture that strung together groups as diverse as the Magyars, Armenians, and Chinese. Under its strong integrating dynamics on the one hand and the impacts of change it transmitted on the other, tribal societies previously living in isolation along the Silk Road or pastoralists who were of barbarian cultural development were drawn to the riches and opportunities of the civilizations connected by the Silk Road, taking on the trades of marauders or mercenaries. Many barbarian tribes became skilled warriors able to conquer rich cities and fertile lands, and forge strong military empires.
The Silk Road gave rise to the clusters of military states of nomadic origins in North China, invited the Nestorian, Manichaean, Buddhist, and Islamic religions into Central Asia and China, created the influential Khazar Federation and at the end of its glory, brought about the largest continental empire ever: the Mongol Empire, with its political centers strung along the Silk Road (Beijing in North China, Karakhorum in eastern Mongolia, Sarmakhand in Transoxonia, Tabriz in Northern Iran, Astrakhan in lower Volga, Bahcesaray in Crimea, Kazan in Central Russia, Erzurum in eastern Anatolia), realizing the political unification of zones previously loosely and intermittently connected by material and cultural goods.
However, the disintegration of the Mongol Empire did not see the continuation of Silk Road's political unity. Also falling victim were the cultural and economic aspects of its unity. Turkmen marching lords seized the western end of the Silk Road, i.e. the decaying Byzantine Empire and sew the seeds of a Turkic culture that would later crystalize into the Ottoman Empire under the Sunni faith. Turkmen and Mongol military bands in Iran, after some years of chaos were united under the Saffavid tribe, under whom the modern Iranian nation took shape under the Shiite faith. Meanwhile Mongol princes in Central Asia were content with Sunni orthodoxy with decentralized princedoms of the Chagatay, Timurid and Uzbek houses. In the Kypchak-Tatar zone, Mongol khanates all but crumbled under the assaults of the Black Death and the rising power of Moscovite. In the east end, the Chinese Ming Dynasty overthrew the Mongol yoke and pursued a policy of economic isolationism (in fact, the Chinese perhaps learned from previous experience that an air of imperial supremacy would better be cultivated without economic and military dependency on Central Asian forces. Hegemonic cultural dynamics had better flow one-way from the imperial center to the periphery, without barbarian elements permeating back into the "great within" of the celestial civilization). Yet another force, the Kalmyk-Oyrats pushed out of the Baikal area in central Siberia, but failed to deliver much impact beyond Turkestan. Some Kalmyk tribes did manage to migrate into the Volga-North Caucasus region, but their impact was limited.
So, in short, great political powers along the Silk Road, after the Mongol Empire, drew frontiers among each other and became economically and culturally cut off from each other. Accompanying the crystallization of regional states was the decline of nomad power, partly due to the devastation of the Black Death, partly due to the encroachment of sedentary civilizations equipped with gun powder. Ironically, the effect of gun power and early modernity on Europe was the integration of territorial states and increasing mercantilism, on the Silk Road it was quite the opposite: failure to maintain the level of integration of the Mongol Empire and decline in trade, partly due to European maritime trade.