A number of conflicts occurred between the Empire and its neighbors. Brazil experienced no serious conflicts with its neighbors to the north and west, due to the buffer of the nearly impenetrable and sparsely populated Amazonian rainforest. In the south, however, the colonial disputes inherited from Portugal and Spain over the control of the navigable rivers and plains which formed the frontiers continued after independence. The lack of mutually agreed borders in this area led to several international conflicts, from the Cisplatine War to the Paraguayan War.