Crusades
The Crusades began as a result of the Seljuk Turks take over of the Holy Lands from the Byzantine Empire in the early 11th century.  The Byzantine emperor asked Pope Urban II of the Roman Catholic Church to help regain these lands for the Christians. The Pope agreed, and over the course of two centuries, thousands of men and women left western Europe to fight to regain these lands. After an initial success, which resulted in the take over of Jerusalem, the rest of the crusades ultimately failed in their original purpose.  However, the impact of the crusades was widespread and very important.

Impact:  The most important impact is the increased trade that resulted from the contact between Christian Europe and the Islamic Empire.  Returning crusaders brought back new spices, foods, perfumes, fabrics and ideas.  Trade was established between the Islamic world and various Italian states, most important among them, the city-state of Venice.  This trade was mutually beneficial, flooding the Islamic markets with a new source of wealth, while bringing such wonders as sugar, cotton, and rice into western Europe.

Resurgence of Europe
The resurgence of Europe begins with the crusades. Various trade items brought back by returning crusaders sparked interest in goods from the east.  Ships that once carried soldiers to the Holy Lands, now began to carry trade goods instead.  This resulted in the growth of Italian City States such as Genoa, Florence, and most importantly Venice in the late 14th century.  Venice formed a strong trade alliance with Egypt, as well as other Muslim states, and soon came to dominate East-West trade.  This was beneficial to both the Venetians and their Islamic counterparts.

Another result of this trade was the growth of trade fairs and cities in western Europe.  The isolated, self-contained manors of Medieval Europe gave way to an interdependent trade network consisting of merchants, artisans, and the rising middle class.  This network exchanged goods and ideas across most of western Europe, establishing most of the major cities of today.

The resurgence of trade following the Middle Ages in Europe resulted in a demand for goods from Asia.  Trade routes were established across the Mediterranean and through the Middle East to handle this need.  But, when the expansion of the Ottoman Empire caused disruption along these routes, Europeans were forced to seek alternative ways of importing these goods.  This led to the exploration of water routes to Asia, and eventually the discovery of the Americas by the Europeans.

While there was a tremendous amount of trade and cultural diffusion during this time period, it is not a time of interdependence, as most aspects of the Age of Exploration and the subsequent period of European Imperialism benefited only Europe, and not any of the indigenous people with whom they were in contact.

Mongols
The Mongols were a nomadic tribe of herders who lived in Central Asia.  Under their greatest leader, Genghis Khan, they conquered the world's largest empire to date.  The Mongols ruled, at one time or another, Russia and parts of Eastern Europe, China, India, and parts of the Middle East.

Mongol Empire

During the Pax Mongolia, or Mongol Peace, global trade expanded due to the political stability provided by Mongol rulers.  Silk Road trade flourished as goods and ideas, such as gunpowder, porcelain, and the technology of papermaking were traded with the west. The interdependence of East and West expanded with the empire.  The stability and relative safety within the empire allowed people such as Marco Polo to travel throughout the many nations.  The writings of Marco Polo introduced the many wonders of China and the Far East to Europeans during the late 13th century.  The Pax Mongolia was a time of trade and cultural diffusion