He left the Tory Party in 1830 to serve with the Whigs as Foreign Secretary (1830–34; 1835–41; 1846–51). In his foreign policy Palmerston was single-minded in his promotion of British interests, declaring the second Opium War against China in 1856, and overseeing the successful conclusion of the Crimean War in 1856 and the suppression of the Indian Mutiny in 1858. He maintained British neutrality during the American Civil War.