Then we must consider the Tokyo napalm raids that killed many more civilians than were killed in Dresden. Is that too something "illegal?"
If someone desires to view events of the war through the distortion of the concept that civilians are somehow magically immune to injury in some fantasy rules of war that never existed save for some peoples' minds, they have failed to immerse themselves in history.
The German war industry began dispersing early on when Allied air attacks began gutting normal factory complexes. It's real easy to target a huge facility that builds Messerschmitts in ONE location. Break that manufacturing system into several parts and place them in clandestined locales that actually increased production after dispersion, and you might as well bomb hell out of everything just to make sure you got the intended target.
This may not apply to Dresden but you get the idea. As we bombed the easily targetable war materiel facilities the Germans dispersed them and production increased!
On March 9, 1945 Lemay began the concerted fire bombing of Japanese cities. Why? Because Jap civvies were makeing war products in their dispersed facilities in Tokyo, Nagoya, Osaka, and Kobe. These raids were effective in that before the next round of napalm attacks leaflets wee dropped waring of the fact and 8.5 million fled to the country to escape frying. With them in out of the urban areas war production nose dived.
And even with that they didn't surrender but prepared a hellatious defensive network of Kyushu and Hokkaido that was to be "last man" mentality.
The Dresden raid was done to please the Russians since they continually complained that they were suffering higher casualties relative to the Allies. Their revengful tactics had a name. It was called "terrorisation." GB was pressured by the Russians to wreak havoc amongst the German civilians.
The initial concept plan for Dresden was not instigated by Harris himself at all. It came from higher up. Can't you picture Churchill being lobbied by Stalin to step up to the plate and "go Russian" on those Nazis?
General Antonov made three specific requests for Allied assistance to the Russians:
a. To speed up the advance of the Allied troops on the Western Front, for which the present situation is very favorable: (1) To defeat the Germans on the Eastern Front. (2) To defeat the German groupings which have advanced into the Ardennes. (3) The weakening of the German forces in the West in connection with the shifting of their reserves to the East (It is desirable to begin the advance during the first half of February).
b. By air action on communications hinder the enemy from carrying out the shifting of his troops to the East from the Western Front, from Norway, and from Italy (In particular, to paralyze the junctions of Berlin and Leipzig).
c. Not permit the enemy to remove his forces from Italy
The Viet Cong used our dislike for seeing innocent civilians injured in Vietnam. I saw daily how they exploited and used them as chattel to sucker us into fights. They had absolutely no conscience about ending their lives so they could get a response from us. This was not isolated but was done on an ongoing, daily basis.
Non-combatants have always been in harm's way in warfare. They've been exploited by either side as they saw fit to gain advantages over their enemy. I say non-combatants and not innocents because many of the adults were engaged in war materiel production. They were contributing to the war effort.
This delusion that in January 1945 the war was all but over is hogwash. Hitler had just pulled off the Ardennes Offensive and we still hadn't landed on Iwo Jima or Okinawa that produced the most horriffic blood letting yet. The kamikazes were doing their thing in the Pacific and more German jets were hammering Allied bombers.
We only know that the war was almost over in a relative sense because we're sitting on our butts 60 here years later. No one knew how long the carnage would go on back then. This is why it is flawed to second guess "what they shoulda done was...."
We never knew then whether our enemies would use bio-chemical warfare as a last ditch effort. It's so easy to look back 60 years and conclude that wasn't a factor worth considering. Believe me it was considered by fighting men in early 1945.
I don't see anyone justifying the Nazi depoyment of V-1 and V-2 rockets that were made ONLY to kill civilians. I don't see anyone imagining that the Germans wouldn't have unleashed vicious bombing attacks on civilians had they possessed a substantial force of heavy bombers either. So why does it makes sense in the turmoil of times and fog of war that this one event was more evil than any other? The Brits were in their 6TH YEAR of eating Nazi crap and they were damned tired of it! Does anyone really believe that some bleating voice of tempering military actions would have been listened to then?
Dresden was the 7th largest Geman city with primary importance as a communications center. It was, in February 1945, known to contain at least 110 factories and industrial enterprises that were legitimate military targets, and were reported to have employed 50,000 workers in arms plants alone. Among these were dispersed aircraft components factories; a poison gas factory (Chemische Fabric Goye and Company); an anti-aircraft and field gun factory (Lehman); the great Zeiss Ikon A.G., Germany's most important optical goods manufactory; and, among others, factories engaged in the production of electrical and X-ray apparatus (Koch and Sterzel A.G.), gears and differentials (Saxoniswerke), and electric gauges (Gebruder Bassler). Specific military installations in Dresden in February 1945 included barracks and hutted camps and at least one munitions storage depot.
The Berlin-Leipzig-Dresden railway complex was a major transportation crossroads logistically involved in the movement of German troops.
Here's the cities by population with the total bomb tonnage expended for the entire war:
Berlin- 4,339,000 67,607.6 tons, Hamberg- 1,129,000 38,687.6 tons,
Munich- 841,000 27,110.9 tons, Cologne 772,000 44,923.2 tons, Leipzig- 707,000 11,616.4 tons, Essen- 667,000 37,938.0 tons, Dresden- 642,000 7,100.5 tons.