We all know about Fort Pillow which angered the Colored Troops. Many of them would advance into battle encouraging each other with the cry, "Remember Fort Pillow." It was the codeword to take no prisoners. This make the Confederates fight even harder when they faced colored troops. In some cases, but for the presence of the white officer or of other (Federal) white troops, the Corn-feds would have been massacred. Here's a tale of one Corn-fed Mason whose life was saved by a Federal Mason at Fort Blakely, Alabama:
"More of our troops were slaid after the surrender than in the battle. Finally the white officers bunched us in squads of forty or fifty each and placed guards around us as close together as they could stand with fixed bayonets facing outward to protect us from the infuriated mob. They continued to shoot our men down, shooting between or over the heads of the guards.
"Captain Adair fell at my side and with a mortal wound. I was cuaght on the outer edge of my squad when I discovered an infuriated Negro about ten feet from me with his gun on me. I stepped behind the guard. He then moved around to one side and back again when I placed the guard between us again.
"At that time a white officer appeared, seeing on his hat the square and compasses [a Masonic symbol] made with a pencil, I gave him a sign which brought him to my side. I pointedout the Negro and asked him to please not let him kill me as I had fought him like a man, surrendered like a man, and would like to be treated like a man.
"He stepped out and struck the Negro on the head with his pistol. The Negro turned and ran up the breastworks. He fired at the Negro and I saw him fall over the breastworks. Shortfly afterward the white office came to my side and asked me if that Negro had bothered me any more. I told him no and was much obliged to him. He whispered to me that he had done three others the same way. This shows that Masonery [sic] will protect a brother even though he be a foe."
Both sides were guilty of killing their prisoners. I've even found an account of a Confederate sharpshooter being killed after surrendering.
Vigilantibus et non dormientibus jura subveniunt. Molon Labe!