Venetian commerce covered the whole civilised world. The city was a great reservoir of merchandise, constantly filled and constantly emptied again, with eastern luxuries flowing westward and western commodities flowing east. Upon export and import alike the government levied taxes (tavola dell1 entrada e tavola deW insidd); these, with the salt monopoly and the taxation of the guilds (tansa delta mttizia, tansa insensibile, etc.), furnished the main source of her ordinary revenue, which in the year 1500 was estimated at 1,145,580 ducats. The importance of the sea in the economy of Venice is obvious; but during the fifteenth century her naval and commercial sea-power both received a fatal blow. Wars with the Turks exhausted her fighting capacity and the discovery of the Cape route to the Indies tended to divert the whole line of the world's traffic from the Mediterranean into the Atlantic, out of the hands of the Venetians into the hands of the Portuguese.
The century opened, however, with a series of triumphs for the Republic. The development and extension of her land empire continued; her prestige at sea increased. Dalmatia, which the Republic had surrendered by the treaty of Turin, was recovered after a struggle; and by 1420 Venice was in possession of the whole of Friuli. Thanks to the mountainous frontier of the province this acquisition gave the Republic a defensible position towards the east, where she had hitherto been very weak; it largely increased her land empire and whetted her appetite for more.
Nor was her achievement by sea less brilliant. The quarrels among the sons of Sultan Bayazid I ended in the concentration of the Ottoman power in the hands of Mohammad (1413). Venice had no desire to embark on a campaign against the victorious Turk. She hoped to trade with them, not to fight them, and, through her ambassador Francesco Foscari, a treaty was signed whereby she believed herself to have secured her colonies from molestation. But Mohammad was not able, even if he desired, to prevent his followers from regarding all Christians as dogs. Treaty or no treaty, they chased some Venetian merchantmen into Negroponte and menaced the island. The Venetian admiral Loredan came to a parley with the Turkish commander, at Gallipoli (1416). But while the leaders were in consultation, the crews fell to, and a battle became inevitable. The Venetians were brilliantly victorious; and the Republic secured an advantageous peace, as well as the applause of Europe, only too ready to believe that it need not mind about the Turk as long as Venice was there to fight him.
But contemporaneously with this fresh expansion of Venice, by the conquest of Friuli and the heightening of her prestige after the victory of Gallipoli, events fraught with grave consequences for the Republic were maturing to the west. On the sudden death of Gian Galeazzo Visconti (1402), his dominions had been seized and partitioned by his generals. Gian Galeazzo's son, Filippo Maria, patiently, slowly, but surely,