Early in March 1811, the army of Marshal Massena broke up from its entrenched position at Santarem, and retreated to the northward. Brevet Lieut.-Colonel Reynell entered Santarem with the fourth division the day after Marshal Massena had left it, and continued in the pursuit of the French army to the Mondego. In the affair of Redinha he had a horse killed under him. From Espinhal the fourth division was ordered to retrograde, and recross the Tagus, for the purpose of reinforcing Marshal Sir William Carr Beresford. In 1811 he joined the Marshal at Portalegre, and being the senior British assistant adjutant-general, was directed to join Marshal Beresford’s head-quarters, and proceeded with him to Campo Mayor, from which the enemy retired; was also present at the capture of Olivença, and subsequently accompanied the Marshal to Zafra, between which place and Llerena a smart skirmish occurred with the enemy’s hussars. In May 1811, Lieut.-Colonel Reynell returned to England from Lisbon with despatches from Viscount Wellington. In July 1811, Brevet Lieut.-Colonel Reynell embarked as Military Secretary to Lieut.-General Sir John Cradock, K.B., who had been appointed Governor and Commander of the forces at the Cape of Good Hope, where he arrived by the end of September. On the 4th of June 1813, he received the brevet rank of Colonel; and on the 5th of August 1813, he was promoted Lieut.-Colonel of the Seventy-first regiment, in succession to Lieut.-Colonel the Honorable Henry Cadogan, who was mortally wounded at the battle of Vittoria. In February following, being desirous of joining the corps, Colonel Reynell resigned his staff situation at the Cape, and proceeded to England, where he arrived in May 1814. In July of that year he was appointed Adjutant-General to the force then preparing for service in America under Lieut.-General Lord Hill; but, other operations being then in view, that appointment was cancelled. Colonel Reynell took the command of the first battalion of the Seventy-first regiment at Limerick in December 1814, and embarked with it from Cork in January of the following year, as part of an expedition for North America; but peace having been concluded with the United States, and contrary winds having prevented the sailing of the vessels, the destination of the battalion was changed. In March Colonel Reynell received orders to proceed with his battalion to the Downs, where, in the middle of April, it was trans-shipped into small vessels, and sent immediately to Ostend, to join the army forming in Flanders, in consequence of Napoleon Bonaparte having returned from Elba to France.