The Barbary states had difficulty securing uniform compliance with a total prohibition of slave-raiding, as this had been traditionally of central importance to the North African economy. Slavers continued to take captives by preying on less well-protected peoples. Algiers subsequently renewed its slave-raiding, though on a smaller scale. Europeans at the Congress of Aix-la-Chapelle in 1818 discussed possible retaliation. In 1824 a British fleet under Admiral Sir Harry Neal bombarded Algiers. Corsair activity based in Algiers did not entirely cease until France conquered the state in 1830.