Baring's military career began with his joining the Hanoverian army in 1787. In November 1803 (dating the commission to 17 November) he became a brevet major in the King's Germans (renamed the King's German Legion on 19 December 1803), a force of which he had been one of the first members. He fought in the campaigns in Hannover (1805, Third Coalition), the Baltic (1807–08, Gunboat War / English Wars), the Pyrenees (1808–13, Peninsular War), the Walcheren Campaign (1809, Fifth Coalition), southern France (1813–14, Sixth Coalition) and the Netherlands (1814, Sixth Coalition). On 16 May 1811 he was slightly wounded at the battle of Albuera. On 18 January 1815 he was promoted to lieutenant colonel.