From Grant's memoirs:
"Longstreet was an entirely different man. He was brave, honest, intelligent, a very capable soldier, subordinate to this superiors, just and kind to his subordinates, but jealous of his own rights, which he had the courage to maintain. He was never on the lookout for a slight, but saw one as soon as anybody when intentionally given.
It may be that Longstreet was not sent to Knoxville for the reason stated, but because Mr. Davis had an exalted opinion of his own military genius, and thought he saw a chance of "killing two birds with one stone." On several occasions during the war he came to the relief of the Union army by means of his superior military genius.
I speak advisedly when I say Mr. Davis prided himself on his military capacity. He says so himself, virtually, in his answer to the notice of his nomination to the Confederate presidency. Some of his generals have said so in their writings since the downfall of the Confederacy."
On Joseph Johnston:
"My own judgement is that Johnston acted very wisely; he hubanded his men and saved as much of his territory as he could, without fighting decisive battles in which all might be lost. As Sherman advanced, as I have shown, his army became spread out, until, if this had continued, it would have been easy to destroy it in detail. I know that Sherman and I were rejoiced when we heard of the change. Hood was unquestionably a brave, gallant soldier and not destitute of ability; but unfortunately his policy ws to fight the enemy wherever he saw him, without thinking much of the consequences of defeat."
Concerning Forrest in Tennessee:
"Forrest had about 4000 cavalry with him, composed of thouroughly well-disciplined men, who under so able a leader were very effective. Smith's command was nearly double that of Forrest, but not equal, man to man, for the lack of successful experience such as Forrest's men had. The fact is, troops who have fought a few battles and won, and followed up their victories, improve upon what they were before to an extent that can hardly be counted by percentage. The difference in result if often a decisive victory instead of inglorious defeat. This same difference, too, is often due to the way troops are officered, and for that particular kind of warfare which Forrest had carried on neither army could present a more effective officer than he was."