Following their capture of Mauritius from the French in 1810 during the Napoleonic Wars, with ownership confirmed by the 1814 Treaty of Paris, the British saw Madagascar as a natural expansion of their influence in the Indian Ocean.
[1] The Merina King, Radama I, managed to unite Madagascar under one rule, benefiting from British weapons and military instructors.
Meanwhile, the Queen's son Prince Rakoto (future King Radama II) had been under the influence of French nationals at Antananarivo.
In 1854, a letter destined for Napoleon III that he dictated and signed was utilized by the French government as a basis for future invasion of Madagascar.
This assassination was treated as successful at the time, although later evidence suggests Radama survived the attack and lived to old age as a regular citizen outside the capital.
[1] In the early 1880s however, the French colonial faction, the right-wing Catholic lobby and Réunion parliamentarians all advocated an invasion of Madagascar in order to suppress British influence there.