Grant's opinion of the Mexican-American War, in which he was a number of times cited for gallantry....

http://www.shotglassofhistory.com/ulysses-s-grant-quote-mexican-american-war/

With a soldier the flag is paramount . . . I know the struggle with my conscience during the Mexican War. I have never altogether forgiven myself for going into that. I had very strong opinions on the subject. I do not think there was ever a more wicked war than that waged by the United States on Mexico. I thought so at the time, when I was a youngster, only I had not moral courage enough to resign. I had taken an oath to serve eight years, unless sooner discharged, and I considered my supreme duty was to my flag.

I had a horror of the Mexican War, and I have always believed that it was on our part most unjust. The wickedness was not in the way our soldiers conducted it, but in the conduct of our government in declaring war. The troops behaved well in Mexico, and the government acted handsomely about the peace. We had no claim on Mexico. Texas had no claim beyond the Nueces River, and yet we pushed on to the Rio Grande and crossed it. I am always ashamed of my country when I think of that invasion.”


"...if the gentlemen of Virginia shall send us a dozen of their sons, we would take great care in their education, instruct them in all we know, and make men of them." Canasatego 1744