for longer periods. In addition double-entry bookkeeping enhanced the possibilities to stretch initiatives into rather far away countries by founding outposts or factories, and by enhancing controlling. Directing activities and intensification of local contacts were facilitated this way, too. Venice as key of world trade between 13th and 15th century The Arabian conquest of Jerusalem caused a long lasting deviation of trade routes to Baghdad and Tabriz. Cilician Armenia was now the main hub of trade. In addition the Venetians lost their main ports in Egypt and in 1291 also the most important Acre. They could only try to make their way through Armenia, Persia, Turkestan. After long and difficult negotiations they were re-admitted in Byzantium. This was very important in so far as sailing through the Bosporus was now the most important way to reach Central Asia. It was not by coincidence that Marco Polo travelled through Asia in these years between 1278 and 1291. A second way led to Trabzon further to the Persian Gulf to India, a third one from Tana at the mouth of the river Don to the Volga and the Caspian Sea to India. But the larger part of trade was conducted by sea-vessels and not overland. Venice so developed a system of regular convoys with strong protective means, but also encouraged private trading. Salt trade The Republic of Venice was active in the production and trading of salt, salted products, and other products along trade routes established by the salt trade. Venice produced its own salt at Chioggia by the seventh century for trade, but eventually moved on to buying and establishing salt production throughout the Eastern Mediterranean. Venetian merchants bought salt and acquired salt production from Egypt, Algeria, the Crimean peninsula, Sardinia, Ibiza, Crete, and Cyprus. The establishment of these trade routes also allow Venetian merchants to pick up other valuable cargo, such as Indian spices, from these ports for trade. They then sold or supplied salt and other goods to cities in the Po Valley - Piacenza, Parma, Reggio, Bologna, among others - in exchange for salami, prosciutto, cheese, soft wheat, and other goods. Venetian exporters were obligated to import salt into Venice, for which they were paid a subsidy - the ordo salis. The Venetian state then resold the salt at a profit - a form of Salt tax - to markets throughout Italy, Dalmatia, Slovenia, and the Stato da