Guise served with his regiment in the Ferrol Expedition, Vigo, and Cadiz in 1800, in Egypt in 1801, in Hanover in 1805–06, and accompanied it to Portugal in 1809. He was present at the Battle of Bussaco, and commanded the light companies of the guards, with some companies of the 95th Rifles attached, at the Battle of Fuentes de Oñoro. He commanded the first battalion 3rd Guards in the Peninsular War of 1812–14, including the Battle of Salamanca, the capture of Madrid, the Siege of Burgos and subsequent retreat, the Battle of Vittoria, the Battle of the Bidassoa, the Battle of the Nive, and the passage of the Adour. At the investment of and repulse of the sortie from Bayonne, he succeeded to the command of the second brigade of Guards when Maj-Gen Edward Stopford was wounded (gold cross and war medal).