In 1340 an Italian guide book is published giving merchants practical advice on the journey. They should let their beards grow, to be inconspicuous in Asia. They will be more comfortable if they hire a woman near the Black Sea to look after their needs on the journey. The assurance that the road is safe has an alarming ring to our ears: 'If you are some sixty men in the company, you will go as safely as if you were in your own house.' But the list of commodities changing hands on the route can be guaranteed to quicken the pulse of any ambitious trader.
Trade with the Mongol east is best known through the adventures of three Italian merchants - Marco Polo, with his father and uncle.
Hanseatic League: 12th - 17th century AD
In 1159 Henry the Lion, duke of Saxony and Bavaria, builds a new German town on a site which he has captured the previous year. It is Lübeck, perfectly placed to benefit from developing trade in the Baltic. Goods from the Netherlands and the Rhineland have their easiest access to the Baltic through Lübeck. For trade in the opposite direction, a short land journey from Lübeck across the base of the Danish peninsula brings goods easily to Hamburg and the North Sea.
Over the next two centuries Lübeck and Hamburg, in alliance, become the twin centres of a network of trading alliances known later as the Hanseatic League.
A Hanse is a guild of merchants. Associations of German merchants develop in the great cities on or near the Baltic (Gdansk, Riga, Novgorod, Stockholm), on the coasts of the North Sea (Bergen, Bremen) and in western cities where the Baltic trade can be profitably brokered - in particular Cologne, Bruges and London.
It suits these German merchants, and the towns which benefit from their efforts, to form mutual alliances to further the flow of trade. Safe passage for everyone's goods is essential. The control of pirates becomes a prime reason for cooperation, together with other measures (such as lighthouses and trained pilots) to improve the safety of shipping.
The rapid growth of Hanseatic trade during the 13th century is part of a general pattern of increasing European prosperity. During this period the towns with active German hanse gradually organize themselves in a more formal league, with membership fees and regular 'diets' to agree policies of mutual benefit. By the 14th century there about 100 such towns, some of them as far afield as Iceland and Spain. Their German communities effectively control the trade of the Baltic and North Sea.
But economic decline during the 14th century takes its toll on the success of the Hanseatic towns. So do political developments around the Baltic.
In 1386 Poland and Lithuania merge, soon winning the region around Gdansk from the Teutonic knights. On the opposite shore of the sea, the three Scandinavian kingdoms are united in 1389; the new monarchy encompasses Stockholm, previously an independent Hanseatic town. A century later, when Ivan III annexes Novgorod, he expels the German merchants.
Such factors contribute to the gradual decline of the Hanseatic League. What began as a positive union to promote trade becomes a restrictive league, attempting to protect German interests against foreign competitors. But great enterprises fade slowly. The final Hanseatic diet is held as late as 1669.
Ups and downs in the economy: 12th - 14th century AD
Throughout Europe the period from about 1150 to 1300 sees a steady increase in prosperity, linked with a rise in population. There are several reasons. More land is brought into cultivation - a process in which the Cistercians play an important part. Rich monasteries, controlled by powerful abbots, become a significant feature of feudal Europe.
In tandem with the improvement in rural wealth is the development of cities thriving on trade, in luxury goods as well as staple products such as wool.
Prominent among the trading centres of the 13th century are the coastal Italian cities, whose merchants ply the Mediterranean; Venice is particularly prosperous after the opportunities presented by the fourth crusade. In a similar way the cities of the Netherlands are well placed to profit from commerce between their three larger neighbours - England, France and the German states. And the Hanseatic towns handle the trade from the Baltic.
Together with this increase in trade goes the development of banking. Christian families, particularly in the towns of northern Italy, begin to amass fortunes by offering the financial services which have previously been the preserve of the Jews.
In the 14th century this economic prosperity falters. Land goes out of cultivation, the volume of trade drops. There are various possible reasons. There is an unusual run of disastrously bad harvests in many areas in the early part of the century. And social structures are painfully adjusting, as the old feudal system of obligations crumbles.
The final straw is the Black Death, which not only kills a third of Europe's population in 1348-9; it also ushers in an era when plague is a recurrent hazard. The 14th century is not the best in which to live. But in the 15th century - the time of the Renaissance in Europe, and the age of exploration - economic conditions improve again.
The Portuguese slave trade: 15th - 17th century AD
The Portuguese expeditions of the 15th century bring European ships for the first time into regular contact with sub-Saharan Africa. This region has long been the source of slaves for the route through the Sahara to the Mediterranean. The arrival of the Portuguese opens up another channel.
Nature even provides a new collection point for this human cargo. The volcanic Cape Verde Islands, with their rocky and forbidding coastlines, are uninhabited. But they contain lush tropical valleys. And they are well placed on the sea routes between West Africa, Europe and America.
Portuguese settlers move into the Cape Verde islands in about 1460. In 1466 they are given an economic advantage which guarantees their prosperity. They are granted a monopoly of a new slave trade. On the coast of Guinea the Portuguese are now setting up trading stations to buy captive Negroes.
Some of these slaves are used to work the settlers' estates in the Cape Verde islands. Others are sent north for sale in Madeira, or in Portugal and Spain - where Seville now becomes an important market. Negroes have been imported by this sea route into Europe since at least 1444, when one of Henry the Navigator's expeditions returns with slaves exchanged for Moorish prisoners.
The labour of the slaves in the Cape Verde Islands primes a profitable trade with the African region which becomes known as Portuguese Guinea or the Slave Coast. The slaves work in the Cape Verde plantations, growing cotton and indigo in the fertile valleys. They are also employed in weaving and dying factories, where these commodities are transformed into cloth.
The cloth is exchanged in Guinea for slaves. And the slaves are sold for cash to the slaving ships which pay regular visits to the Cape Verde Islands.
This African trade, together with the prosperity of the Cape Verde Islands, expands greatly with the development of labour-intensive plantations growing sugar, cotton and tobacco in the Caribbean and America. The Portuguese enforce a monopoly of the transport of African slaves to their own colony of Brazil. But other nations with transatlantic interests soon become the main visitors to the Slave Coast.
By the 18th century the majority of the ships carrying out this appalling commerce are British. They waste no part of their journey, having evolved the procedure known as the triangular trade.
Jacques Coeur, merchant: AD 1432-1451
The career of Jacques Coeur vividly suggests the opportunities open to an enterprising merchant in the 15th century. The greatest source of trading wealth is the Mediterranean, linking Christian markets in the west with Muslim ones in the east - known at this time as the Levant, the land of the rising sun.
Jacques Coeur enters this trade in 1432. He soon has seven galleys taking European cloth to the Levant and bringing back oriental spices. At Montpellier he builds a great warehouse to form the centre of his trading operation.
Agents promote Jacques Coeur's business from a string of offices which link the Mediterranean source of his wealth with the markets of western Europe. He is represented in Barcelona, Avignon, Lyons, Paris, Rouen and Bruges.
Rapid commercial success and a marked political talent soon bring Jacques Coeur influence in government. Master of the mint in Paris from 1436, he is put in charge of royal expenditure three years later. In 1441 he is ennobled. In 1442 he becomes a member of the king's council.
These are heady years in which to be close to the French court, as Charles VII recovers his kingdom in the closing stages of the Hundred Years' War. The king returns at last to Paris in 1437, the year after Jacques Coeur's appointment to head the royal mint in the capital city. When Charles wins Normandy in 1450, he is financed by a large loan from his commercial friend. Jacques Coeur enters Rouen in pomp and ceremony beside the king.
Meanwhile in Bourges, where for so many years Charles VII held his court, the merchant has built himself a house fit for a king. The Palace of Jacques Coeur, still surviving, is a spectacular example of 15th-century domestic architecture.
Such conspicuous wealth and power in an upstart brings its own dangers. Jacques Coeur has lent large sums to many in court circles. Greed and envy alike prompt his ruin. The king is persuaded that Jacques Coeur is guilty of various financial crimes and may even be responsible for the death of Charles's mistress, Agnès Sorel, in 1450.
Jacques Coeur is arrested and imprisoned in 1451. He escapes two years later and makes his way to Rome to serve the pope. All his possessions have been confiscated. Nothing survives of the mighty merchant's kingdom. Jacques Coeur's story reflects the dangers of the age - but also, even more abundantly, its opportunities.
Chinese sea trade: 15th century
The greatest extent of Chinese trade is achieved in the early 15th century when Zheng He, a Muslim eunuch, sails far and wide with a fleet of large junks. At various times between 1405 and 1433 he reaches the Persian Gulf, the coast of Africa (returning with a giraffe on board) and possibly even Australia.
Typical Chinese exports are now porcelain, lacquer, silks, items of gold and silver, and medicinal preparations. The junks return with herbs, spices, ivory, rhinoceros horn, rare varieties of wood, jewels, cotton and ingredients for making dyes.
Europe's inland waterways: 15th-17th century AD
Trade up and down great rivers and in coastal waters is as old as civilization. Trade across seas develops as soon as adequate boats are built, most notably by the Phoenicians. The natural next stage is to join river systems and even seas by man-made canals. Pioneered in Egypt and China in very ancient times, this development does not occur in Europe until the 15th century AD.
With prosperity beginning to pick up after the depression following the Black Death, merchants have need of cheap and reliable transport. Europe's roads are rutted tracks, the use of which is slow and dangerous. There is good commercial reason to connect the rivers, the arteries of trade. The merchants of Lübeck take the first step.
From 1391 the Stecknitz canal is constructed southwards from the city of Lübeck. Its destination is the Elbe, which is reached early in the 15th century. The new waterway joins the Baltic to the North Sea.
This canal rises some 40 feet from Lübeck to the region of Möllner and then falls the same amount again to reach the Elbe, all in a distance of 36 miles. This must be about the limit which can be safely achieved with flash locks. With mitre locks, from the 16th century, anything is possible. And the most ambitious projects are undertaken in France.
The Briare canal, completed in 1642, joins the Seine to the Loire; at one point it has a staircase of six consecutive locks to cope with a descent of 65 feet over a short distance. Even more remarkable is the Canal du Midi, completed in 1681, which joins the Mediterranean to the Atlantic by means of 150 miles of man-made waterway linking the Aude and Garonne rivers. At one point this canal descends 206 feet in 32 miles; three aqueducts are constructed to carry it over rivers; a tunnel 180 yards long pierces through one patch of high ground.
The potential of canals is self-evident. It falls to Britain, in the next century, to construct the first integrated system of waterborne traffic.
Portugal's eastern trade: AD 1508-1595
The profitable trade in eastern spices is cornered by the Portuguese in the 16th century to the detriment of Venice, which has previously had a virtual monopoly of these valuable commodities - until now brought overland through India and Arabia, and then across the Mediterranean by the Venetians for distribution in western Europe.
By establishing the sea route round the Cape, Portugal can undercut the Venetian trade with its profusion of middlemen. The new route is firmly secured for Portugal by the activities of Afonso de Albuquerque, who takes up his duties as the Portuguese viceroy of India in 1508.
The early explorers up the east Africa coast have left Portugal with bases in Mozambique and Zanzibar. Albuquerque extends this secure route eastwards by capturing and fortifying Hormuz at the mouth of the Persian Gulf in 1514, Goa on the west coast of India in 1510 (where he massacres the entire Muslim population for the effrontery of resisting him) and Malacca, guarding the narrowest channel of the route east, in 1511.
The island of Bombay is ceded to the Portuguese in 1534. An early Portuguese presence in Sri Lanka is steadily increased during the century. And in 1557 Portuguese merchants establish a colony on the island of Macao. Goa functions from the start as the capital of Portuguese India.
Rivals in the overseas trade: AD 1555-1595
With this chain of fortified ports of call, and with no vessels in the Indian Ocean capable of challenging her power at sea, Portugal has a monopoly of the eastern spice trade.
Indeed the English, now developing interests of their own in ocean commerce, consider that their only hope of trade with the far east is to find a route north of Russia. One of the first joint-stock enterprises, the Muscovy Company chartered in 1555, results from early efforts to find a northeast passage.
Of the other Atlantic maritime powers, Spain is mainly occupied with its American responsibilities. And the Dutch enjoy a direct benefit from Portugal's trade. Their ships have a monopoly in ferrying the precious eastern cargoes from Lisbon to northern Europe.
The situation changes suddenly in 1580, when the Spanish (perennial enemies of the Dutch) occupy Portugal.
The Spanish leave control of the Portuguese empire to Lisbon, but the political change in itself does damage to Portugal's trading interests. Deprived now of their share of the eastern trade, the Dutch resolve to build up a commerce of their own. Like the English, their first instinct is to look for a northeast passage (a task which takes Willem Barents into uncharted waters). But in 1595 they decide that their best course of action is to challenge the Portuguese on the southern route.
It is a decision which will lead to major changes in the eastern trade. But in the short term, the greater volume of trade is now being carried out by Spain across the Atlantic.