Anglo-Portuguese Treaty, 1891.
Following the disturbances on the Mashonaland border, where a collision had taken place between Portuguese troops and British South African Police, an ultimatum was despatched to Portugal, demanding the withdrawal of her troops from the disputed territory. A treaty was subsequently signed delimiting the spheres of influence of the two Powers and declaring the navigation of the Shiré and the Zambesi open to all nations, while Portugal agreed to facilitate communication by these and other river and land routes.