Brodrick entered the navy about 1723. In 1739 he was a lieutenant of , Admiral Edward Vernon's flagship at the Battle of Porto Bello, and commanded the landing party which stormed the Castillo de Fierro. In recompense for his brilliant conduct Vernon promoted him to the command of the fireship , in which he in 1741 took part in the Battle of Cartagena de Indias. On 25 March 1741 he was "posted" (i.e. made Post Captain) into the frigate , and continued actively employed during the rest of that campaign, and afterwards in the expedition to Cuba. After other service he returned to England in 1743, and early in the following year was appointed to the 60-gun . In March of the following year he was appointed to , which was sent out to the Leeward Islands, and continued there until after the peace in 1748.