In the memorable battle of Waterloo, fought on the 18th of June 1815, Colonel Reynell commanded the first battalion of the Seventy-first regiment, and was wounded in the foot on that occasion. He afterwards succeeded to the command of Major-General Adam’s brigade, consisting of the first battalions of the Fifty-second and Seventy-first, with six companies of the second, and two companies of the third battalion of the Ninety-fifth regiment, in consequence of that officer being wounded. Colonel Reynell commanded the light brigade in the several operations that took place on the route to Paris, and entered that capital at the head of the brigade on the 7th of July 1815, and encamped with it in the _Champs Elysées_, being the only British troops quartered within the barriers. In this year he was appointed a Companion of the Order of the Bath, and received the Cross of a Knight of the Austrian Military Order of Maria Theresa, also a Cross of the fourth class of the Russian Military Order of St. George. Colonel Reynell remained with the “_Army of Occupation_” in France until October 1818, when, after a grand review of the united British, Danish, and Russian contingents at Valenciennes, the Seventy-first marched to Calais, and embarked for England. Colonel Reynell continued in command of the regiment until the 12th of August 1819, the date of his promotion to the rank of Major-General. In April 1820 Major-General Reynell was suddenly ordered to proceed to Glasgow, having been appointed to the staff of North Britain as a Major-General, in which country he remained until March 1821, when, in consequence of the tranquillity of Scotland, the extra general officer was discontinued. Immediately after he was appointed to the staff of the East Indies, and directed to proceed to Bombay, for which presidency he embarked in September following, and where he arrived in March 1822. After remaining there a month, Major-General Reynell was removed to the staff of the Bengal Presidency, by order of the Marquis of Hastings. In August Major-General Reynell proceeded up the Ganges, and took the command of the Meerut division on the 3rd of December 1822. The next operation of importance in which Major-General Reynell was engaged was the siege of _Bhurtpore_. Early in December 1825 a large force had been assembled for this purpose, to the command of which he had been appointed, when, just as the troops were about to move into the Bhurtpore states, General Lord Combermere, the new Commander-in-Chief in India, arrived from England, and Major-General Reynell was then appointed to command the first division of infantry. He commanded that division during the siege, and directed the movements of the column of assault at the north-east angle on the 18th of January 1826, when the place was carried, and the citadel surrendered a few hours after. For this service he was appointed a Knight Commander of the Bath, as well as honored with the thanks of both Houses of Parliament.