Why did Portugal have to accept Britain’s definition of Mozambique’s western and southern boundaries in 1891?

In 1891, Portugal was compelled to accept Britain’s definition of Mozambique’s western and southern boundaries primarily due to a significant power imbalance and economic leverage.

At the time, the Portuguese crown was heavily indebted to British financiers, making the nation financially vulnerable. Furthermore, Portugal’s military capabilities were no match for those of Britain. This tension was exacerbated by the 1890 British ultimatum, which demanded the withdrawal of Portuguese forces from disputed regions in central Africa and implicitly threatened the use of British naval force, as well as the potential dissolution of the long-standing Anglo-Portuguese alliance.123

Faced with these pressures, Portugal was unable to maintain its expansive territorial claims—such as the "Rose-Coloured Map" that sought to connect Angola and Mozambique—and ultimately conceded to British demands regarding its colonial borders.132