With commerce ascendant, the to-and-fro of conquest, pillage, and trade continued apace, centered between Italy and the Levant. The Venetians and Byzantine Empire had been trading since the empire was founded. In the 11th century the Venetians secured a commercial coup in return for aid against the Seljuk Turks: duty-free port access throughout the empire, a privilege that native merchants lacked.
Meanwhile, Genoa and Pisa drove the Muslims off the islands of Corsica and Sardinia, attacked and looted their north Africa strongholds, and then extracted most-favored trading status for themselves.
The Crusades were a series of Christian assaults against various targets, including a pogrom against endemic Jews in Europe during the upswing to the 1st Crusade at the end of the 11th century. Though billed by the papacy as reclaiming the Holy Land (and other conveniently located territories), the Crusades were essentially overelaborated looting sorties that failed more often than not. Regardless of outcome, in the aftermath the Italians made the necessary treaties with Muslims which ensured that trading continued.
Some of the most exotic wares to Europe in the 13th to mid-14th century came from China, and, to a much lesser degree, India. Again, Italians dominated the trade.
The Mongol rulers, despite their reputation for ferocity, welcomed Christian missionaries and Western traders. The crusade there was strictly commercial.
As early as the 12th century, regional specialization in producing various goods occurred. The most famous example was wine from Bordeaux, but grain from the Baltic lands increasingly fed the urban Low Countries, and Flemish weavers relied upon raw wool from England.