In February, 1814, he led six thousand men at the passage of the Gaves, and was engaged in all the operations on the Lower Pyrenees with the Spaniards under the Prince of Anglona. He served in that victorious campaign which terminated at the blood-stained hill of Toulouse, where, as General Napier so pithily remarks, "the war terminated, _and with it all remembrance of the veterans' services_." In the Constitutional war which ensued in Spain nine years after, and during the invasion of that country by monarchical France in 1823, the O'Donnels bore a prominent part, and adhered to Ferdinand VII. The Conde de Abispal was appointed a field-marshal, with the office of governor and political chief at Madrid, and on the 25th March he issued a proclamation announcing that the amnesty granted by the Cortes to those in arms against the king was about to expire, and concluded by a brief warning to the factious and the Constitutionalists to lay down their arms. On the 17th April he published his able orders and propositions to the militia of the capital, together with the following declaration of his political principles:-- "_Don Henry O'Donnel, Knight Grand Cross, &c., General of the 3rd Corps, &c._ "Having learned that some ill-disposed persons have confounded my _private opinion_ with those sacred obligations _which my oath and duty impose upon me_, and have given out that I am unwilling to support the Constitution of 1812 even to the last extremity, and until the national representation, lawfully constituted, should have made certain changes therein; I do declare that _I am resolved to defend it_, according to my oath, until it shall be altered by those means which the Constitution itself prescribes, and that I deem as traitors all Spaniards who, deviating from the path of duty traced out by law, shall cease to obey the same. Such were my sentiments when, in answer to an address from M. Montijo, I wrote a letter which they charge me with having published, and such will ever be my sentiments. But my _opinion_ as an individual shall never prevent me from fulfilling my _duty_ as a general and a citizen of Spain. "Madrid, 17th May, 1823." But ere long he found the difficulty of reconciling his private sentiments and conviction with his duty to a king who had become the tool of France. Abispal proved the Talleyrand of Spain, and lost all favour by his indecision and vacillation; for, after receiving the Grand Cordon of the Order of Carlos III. from the hands of Ferdinand VII., he passed over to the Constitutionalists. From that day his power declined, and he was glad to seek shelter from the fury and clamour of the people at Montpelier in France, where he lived in retirement and much reduced in circumstances.