Two monarchs played key roles in establishing Merina political dominance over Madagascar. The first, who ruled under the name of Andrianampoinimerina (r. 1797-1810), seized the throne of one of the Merina kingdoms in 1787. By 1806 he had conquered the remaining three kingdoms and united them within the former boundaries of Imerina, the capital established at the fortified city of Antananarivo. Radama I (r. 1816-28), an able and forward-looking monarch, succeeded to the throne in 1810 upon the death of his father. By adroitly playing off competing British and French interests in the island, he was able to extend Merina authority over nearly the entire island of Madagascar. Radama I first conquered the Betsileo ethnic group in the southern part of the central highlands and subsequently overpowered the Sakalava, an ethnic group that also sought at times to assert its hegemony over other groups. With the help of the British, who wanted a strong kingdom to offset French influence, Radama I modernized the armed forces. In 1817 the peoples of the east coast, facing an army of 35,000 soldiers, submitted with little or no protest; Radama then conquered the entire southeast as far as Tolagnaro. Particularly barren or impenetrable parts of the island escaped conquest, especially in the extreme south, but before his death Radama I succeeded in bringing the major and more hospitable portions of the country under Merina rule.