I've posted about this incident before. The Jews and the Muslims are blood enemies:
https://en.wikipedia.org/wiki/Banu_Qurayza
Then they surrendered, and the apostle confined them in Medina in the quarter of d. al-Harith, a woman of B. al-Najjar. Then the apostle went out to the market of Medina (which is still its market today) and dug trenches in it. Then he sent for them and struck off their heads in those trenches as they were brought out to him in batches. Among them was the enemy of Allah Huyayy b. Akhtab and Ka`b b. Asad their chief. There were 600 or 700 in all, though some put the figure as high as 800 or 900. As they were being taken out in batches to the apostle they asked Ka`b what he thought would be done with them. He replied, "Will you never understand? Don't you see that the summoner never stops and those who are taken away do not return? By Allah it is death!" This went on until the apostle made an end of them. Huyayy was brought out wearing a flowered robe in which he had made holes about the size of the finger-tips in every part so that it should not be taken from him as spoil, with his hands bound to his neck by a rope. When he saw the apostle he said, "By God, I do not blame myself for opposing you, but he who forsakes God will be forsaken." Then he went to the men and said, "God's command is right. A book and a decree, and massacre have been written against the Sons of Israel." Then he sat down and his head was struck off
There are several more instances of Mohammed over running a village and executing most of the men.
