A discussion about the Eugenics Wars over in the Unpopular Opinions thread made me decide to look up exactly what was established about them in "Space Seed." We're given just a few tantalizing references, giving us a rough outline of the war(s), but it seems fairly clear that they were pretty devastating. (Pertinent dialogue quoted below, with certain lines bolded for emphasis.)
Now, it seems fairly clear that when "Space Seed" was written, the Eugenics Wars and WWIII were supposed to be one and the same thing. This was rather quickly retconned when The Next Generation came along in 1987, as I'd imagine that the mid-90s date given in "Space Seed" started to feel a little too close for comfort. So in "Encounter at Farpoint," we're told that WWIII took place in the 21st century, and that various factions controlled their military forces through narcotics. Eventually, enough details were added that it was clear that now WWIII was now considered to be an entirely separate thing from the Eugenics Wars, as WWIII took place from 2026 to 2053 and involved a nuclear exchange between nations.
On Memory Alpha, I found this intriguing theory:

I also found it interesting to discover that, when I double-checked the dialogue from "Space Seed," they never actually refer to the Eugenics Wars as "World War III" in the episode. It's merely "the last of your so-called World Wars." This gives us another tantalizing possibility, that maybe there was another World War between WWII and the Eugenics Wars in the mid-1990s. Did the creators of "Space Seed" possibly envision Earth having a Third World War in the 70s or 80s, with WWIV happening in the 90s as the Eugenics Wars?
And in looking up info for this post, I learned that there was a deleted scene from "The Corbomite Maneuver" where it was implied that World War III was actually avoided after Earth came very close to it at the time of the "Sino-Western trouble."
What do you think, folks? How do you envision World War III and/or the Eugenics Wars as happening in the history of the TOS era? And do you consider them to be the same thing or not?
SPOCK: Records of that period are fragmentary, however. The mid-1990s was the era of your last so-called World War.
MCCOY: The Eugenics Wars.
SPOCK: Of course. Your attempt to improve the race through selective breeding.
MCCOY: Now, wait a minute. Not our attempt, Mister Spock. A group of ambitious scientists. I'm sure you know the type. Devoted to logic, completely unemotional--
KIRK: There are a great many unanswered questions about those years.
SPOCK: A strange, violent period in your history. I find no record what so ever of an SS Botany Bay. Captain, the DY-100 class vessel was designed for interplanetary travel only. With simple nuclear-powered engines, star travel was considered impractical at that time. It was ten thousand to one against their making it to another star system. And why no record of the trip?
KIRK: Botany Bay... That was the name of a penal colony on shores of Australia, wasn't it? If they took that name for their vessel--
SPOCK: If you're suggesting this was a penal deportation vessel, you've arrived at a totally illogical conclusion.
KIRK: Oh?
SPOCK: Your Earth was on the verge of a dark ages. Whole populations were being bombed out of existence. A group of criminals could have been dealt with far more efficiently than wasting one of their most advanced spaceships.
KIRK: Yes. So much for my theory. I'm still waiting to hear yours.
KIRK: Would you estimate him to be a product of selective breeding?
SPOCK: There is that possibility, Captain. His age would be correct. In 1993, a group of these young supermen did seize power simultaneously in over forty nations.
KIRK: Well, they were hardly supermen. They were aggressive, arrogant. They began to battle among themselves.
SPOCK: Because the scientists overlooked one fact. Superior ability breeds superior ambition.
KIRK: Interesting, if true. They created a group of Alexanders, Napoleons.
SPOCK: I have collected some names and made some counts. By my estimate, there were some eighty or ninety of these young supermen unaccounted for when they were finally defeated.
KIRK: That fact isn't in the history texts.
SPOCK: Would you reveal to war-weary populations that some eighty Napoleons might still be alive?
KIRK: Forgive my curiosity, Mister Khan, but my officers are anxious to know more about your extraordinary journey.
SPOCK: And how you managed to keep it out of the history books.
KHAN: Adventure, Captain. Adventure. There was little else left on Earth.
SPOCK: There was the war to end tyranny. Many considered that a noble effort.
KHAN: Tyranny, sir? Or an attempt to unify humanity?
SPOCK: Unify, sir? Like a team of animals under one whip?
KHAN: I know something of those years. Remember, it was a time of great dreams, of great aspiration.
SPOCK: Under dozens of petty dictatorships.
KHAN: One man would have ruled eventually. As Rome under Caesar. Think of its accomplishments.
SPOCK: Then your sympathies were with--
KHAN: You are an excellent tactician, Captain. You let your second in command attack while you sit and watch for weakness.
KIRK: You have a tendency to express ideas in military terms, Mister Khan. This is a social occasion.
KHAN: It has been said that social occasions are only warfare concealed. Many prefer it more honest, more open.
KIRK: You fled. Why? Were you afraid?
KHAN: I've never been afraid.
KIRK: But you left at the very time mankind needed courage.
KHAN: We offered the world order!
KIRK: We?
KIRK: Khan Noonien Singh.
SPOCK: From 1992 through 1996, absolute ruler of more than a quarter of your world. From Asia through the Middle East.
MCCOY: The last of the tyrants to be overthrown.
SCOTT: I must confess, gentlemen. I've always held a sneaking admiration for this one.
KIRK: He was the best of the tyrants and the most dangerous. They were supermen, in a sense. Stronger, braver, certainly more ambitious, more daring.
SPOCK: Gentlemen, this romanticism about a ruthless dictator is
KIRK: Mister Spock, we humans have a streak of barbarism in us. Appalling, but there, nevertheless.
SCOTT: There were no massacres under his rule.
SPOCK: And as little freedom.
MCCOY: No wars until he was attacked.
SPOCK: Gentlemen.
KIRK: Mister Spock, you misunderstand us. We can be against him and admire him all at the same time.
SPOCK: Illogical.
KIRK: Totally.
MCCOY: The Eugenics Wars.
SPOCK: Of course. Your attempt to improve the race through selective breeding.
MCCOY: Now, wait a minute. Not our attempt, Mister Spock. A group of ambitious scientists. I'm sure you know the type. Devoted to logic, completely unemotional--
KIRK: There are a great many unanswered questions about those years.
SPOCK: A strange, violent period in your history. I find no record what so ever of an SS Botany Bay. Captain, the DY-100 class vessel was designed for interplanetary travel only. With simple nuclear-powered engines, star travel was considered impractical at that time. It was ten thousand to one against their making it to another star system. And why no record of the trip?
KIRK: Botany Bay... That was the name of a penal colony on shores of Australia, wasn't it? If they took that name for their vessel--
SPOCK: If you're suggesting this was a penal deportation vessel, you've arrived at a totally illogical conclusion.
KIRK: Oh?
SPOCK: Your Earth was on the verge of a dark ages. Whole populations were being bombed out of existence. A group of criminals could have been dealt with far more efficiently than wasting one of their most advanced spaceships.
KIRK: Yes. So much for my theory. I'm still waiting to hear yours.
KIRK: Would you estimate him to be a product of selective breeding?
SPOCK: There is that possibility, Captain. His age would be correct. In 1993, a group of these young supermen did seize power simultaneously in over forty nations.
KIRK: Well, they were hardly supermen. They were aggressive, arrogant. They began to battle among themselves.
SPOCK: Because the scientists overlooked one fact. Superior ability breeds superior ambition.
KIRK: Interesting, if true. They created a group of Alexanders, Napoleons.
SPOCK: I have collected some names and made some counts. By my estimate, there were some eighty or ninety of these young supermen unaccounted for when they were finally defeated.
KIRK: That fact isn't in the history texts.
SPOCK: Would you reveal to war-weary populations that some eighty Napoleons might still be alive?
KIRK: Forgive my curiosity, Mister Khan, but my officers are anxious to know more about your extraordinary journey.
SPOCK: And how you managed to keep it out of the history books.
KHAN: Adventure, Captain. Adventure. There was little else left on Earth.
SPOCK: There was the war to end tyranny. Many considered that a noble effort.
KHAN: Tyranny, sir? Or an attempt to unify humanity?
SPOCK: Unify, sir? Like a team of animals under one whip?
KHAN: I know something of those years. Remember, it was a time of great dreams, of great aspiration.
SPOCK: Under dozens of petty dictatorships.
KHAN: One man would have ruled eventually. As Rome under Caesar. Think of its accomplishments.
SPOCK: Then your sympathies were with--
KHAN: You are an excellent tactician, Captain. You let your second in command attack while you sit and watch for weakness.
KIRK: You have a tendency to express ideas in military terms, Mister Khan. This is a social occasion.
KHAN: It has been said that social occasions are only warfare concealed. Many prefer it more honest, more open.
KIRK: You fled. Why? Were you afraid?
KHAN: I've never been afraid.
KIRK: But you left at the very time mankind needed courage.
KHAN: We offered the world order!
KIRK: We?
KIRK: Khan Noonien Singh.
SPOCK: From 1992 through 1996, absolute ruler of more than a quarter of your world. From Asia through the Middle East.
MCCOY: The last of the tyrants to be overthrown.
SCOTT: I must confess, gentlemen. I've always held a sneaking admiration for this one.
KIRK: He was the best of the tyrants and the most dangerous. They were supermen, in a sense. Stronger, braver, certainly more ambitious, more daring.
SPOCK: Gentlemen, this romanticism about a ruthless dictator is
KIRK: Mister Spock, we humans have a streak of barbarism in us. Appalling, but there, nevertheless.
SCOTT: There were no massacres under his rule.
SPOCK: And as little freedom.
MCCOY: No wars until he was attacked.
SPOCK: Gentlemen.
KIRK: Mister Spock, you misunderstand us. We can be against him and admire him all at the same time.
SPOCK: Illogical.
KIRK: Totally.
Now, it seems fairly clear that when "Space Seed" was written, the Eugenics Wars and WWIII were supposed to be one and the same thing. This was rather quickly retconned when The Next Generation came along in 1987, as I'd imagine that the mid-90s date given in "Space Seed" started to feel a little too close for comfort. So in "Encounter at Farpoint," we're told that WWIII took place in the 21st century, and that various factions controlled their military forces through narcotics. Eventually, enough details were added that it was clear that now WWIII was now considered to be an entirely separate thing from the Eugenics Wars, as WWIII took place from 2026 to 2053 and involved a nuclear exchange between nations.
On Memory Alpha, I found this intriguing theory:
I like this theory a lot, as it's a simple rationalization for the casualty numbers for WWI and WWII being so off. (And if there's one thing that Spock typically gets right, it's numbers.)In TOS: "Bread and Circuses", Spock states that eleven million people died in World War II. This, however, severely contradicts current data, which places the death toll anywhere from a low of twenty million (if only military is counted) to a high of over seventy million (if military and civilians are counted). Most counts settle on around fifty million or so.
Spock may have been referring solely to civilian casualties as a result of "slavery" and "despotism" rather than the total war itself. Eleven million is a number frequently given for civilian deaths solely from Nazi policies. This might explain a figure of six million that he gave for World War I, too, as that is about an average (slightly on the low side) estimate of civilian deaths out of a World War I total of about sixteen million.

I also found it interesting to discover that, when I double-checked the dialogue from "Space Seed," they never actually refer to the Eugenics Wars as "World War III" in the episode. It's merely "the last of your so-called World Wars." This gives us another tantalizing possibility, that maybe there was another World War between WWII and the Eugenics Wars in the mid-1990s. Did the creators of "Space Seed" possibly envision Earth having a Third World War in the 70s or 80s, with WWIV happening in the 90s as the Eugenics Wars?
And in looking up info for this post, I learned that there was a deleted scene from "The Corbomite Maneuver" where it was implied that World War III was actually avoided after Earth came very close to it at the time of the "Sino-Western trouble."
What do you think, folks? How do you envision World War III and/or the Eugenics Wars as happening in the history of the TOS era? And do you consider them to be the same thing or not?