In the two periods of weak European growth, growth in maritime trade in the overseas regions was not particularly spectacular either. On the contrary, during the great depression in the 14th and 15th centuries, the conquests of the Turks and, in particular, the Mongol Tatars deprived European trade of access to important markets in the Levant . During the second period of weak economic growth in the late 17th and early 18th centuries, European overseas trade did not begin to expand significantly again until after the Portuguese-Spanish colonial empire had been replaced by the Dutch-British empire. This involved a certain shift of geographical focus, but it was essentially based on simple trade and exchange at garrisons and coastal bases, as well as plantation agriculture, which bore characteristics of slash-and-burn economics. In other words, colonial expansion also remained an économie du pourtour .