In a famous exchange, Mark Twain attacked Matthew Arnold for imagined slights made upon Grant's Memoirs in Arnold's two-part article in Murray's Magazine of 1886. As usual, Twain was amusing and a bit unfair. Although Arnold indulges in some grammatical quibbles and miscellaneous snide remarks on Americans in general, he pays great tribute to Grant. He admits to a mistaken impression that the General was "a strong, resolute, business-like man, who by possession of unlimited resources in men and money, and by the unsparing use of them, had been enabled to wear down and exhaust the strength of the South." Although this misimpression is still a commonplace in the late twentieth century, Arnold is convinced after perusing the Memoirs that it is most fair to compare Grant with the Duke of Wellington.

Wholly free from show, parade, and pomposity; sensible and sagacious; scanning closely the situation, seeing things as they actually were, then making up his mind as to the right thing to be done under the circumstances, and doing it; never flurried, never vacillating, but also not stubborn.

Such praise would have pleased Grant, for he disliked the frequent comparisons made between Napoleon (whom he felt to be great but unprincipled) and himself. He much preferred to be compared with Napoleon's conqueror. Yet in his praise Arnold is compelled to admit that his initial reaction to Grant's Memoirs was conditioned by the fact that, "the central figure ...is not to the English imagination the hero of the American Civil War; the hero is Lee."