To prove my point, I will used the Axis city of Dresden as my example. Dresden had been largely untouched during the war. It had one of the few functional rail and communications centre. Gasmasks and gunsights were made in a lot of the factories. Dresden was a very defended city. Their was no singling out, and t he purpose was not to terrorize the German populace. This raid did not use extraordinary means. It was similar to other raids in this time frame, to similar targets. It achieved military objective without too much loss of life. This raid was carried out through the regular command and they didn't break any military rules. The mayor of Dresden thought that he would be quite safe, and lacked preparation to practice evacuation in the case of an air raid. Another city, Braunschweig was bombed, highly trained firefighter and bunkers saved the lives of 23,000 people from dying in the firestorm. War is not fun and games, and there must be serious measures taken, if it will ever end. That is also how WW2 ended, sadly because of the Hiroshima and Nagasaki. This was the new generation of atomic and nuclear bombs.
According to the KJV Bible, in the Ten Commandments, it says 'Thou Shalt Not Kill."
there are different options such as peaceful agreements to end the war, find and do something about the root of the problem, for example - Hitler was the root of the problem in WWII. If we (allies) had found him and asked him to sign peace treaties or sent to prison for the rest of his life, his people and armies would've lost their idol and hero. They would most likely surrender.
What happened is in the past so we can't change it but we can learn from our mistakes.