Given how inaccurate Spock is about the deaths in the first and second world wars, the numbers for the third are probably no better.
Isn't it more "logical" to assume that
Star Trek happens in an alternate universe which had different events in its World Wars, so that they had different numbers of fatalities, than to assume that Spock could be so inaccurate about the number of fatalities in the known world wars?
The information about the world wars is not very extensive.
In "Space Seed":
SPOCK: No such vessel listed. 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
The mid 1990s in the calendar used in "Space Seed" should go from 1993.33 SS to 1996.66 SS.
So according to the textbooks used by Spock, the Eugenics Wars was the latest Earth conflict that qualified as one of the World Wars. So whether the Eugenics Wars were designated World War Three or World War Thirty Three, or had some other number on Spock's list of world wars on Earth, they were considered the last world war on Earth.
Spock later describes the era of the Eugenics Wars:
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.
Whole populations being bombed out of existence implies the use of ICBMs with nuclear warheads.
In "The City on the Edge of Forever" the Second World War is identified as the one with Hitler and the Nazis:
SPOCK: This is how history went after McCoy changed it. Here, in the late 1930s. A growing pacifist movement whose influence delayed the United States' entry into the Second World War. While peace negotiations dragged on, Germany had time to complete its heavy-water experiments.
KIRK: Germany. Fascism. Hitler. They won the Second World War.
SPOCK: Because all this lets them develop the A-bomb first. There's no mistake, Captain. Let me run it again. Edith Keeler. Founder of the peace movement.
KIRK: But she was right. Peace was the way.
SPOCK: She was right, but at the wrong time. With the A-bomb, and with their V2 rockets to carry them, Germany captured the world.
KIRK: No.
SPOCK: And all this because McCoy came back and somehow kept her from dying in a street accident as she was meant to. We must stop him, Jim.
So according to the list of Earth's world wars used by Kirk and Spock, the Second World War was the one that lasted from 1939 to 1945 in our history. That implies that the First World War on their list was probably the war that lasted from 1914 to 1918 in our history.
In "Bread and Circuses":
SPOCK: I said I understood it, Doctor. I find the checks and balances of this civilisation quite illuminating.
MCCOY: Next he'll be telling us he prefers it over Earth history.
SPOCK: They do seem to have escaped the carnage of your first three world wars, Doctor.
MCCOY: They have slavery, gladiatorial games, despotism.
SPOCK: Situations quite familiar to the six million who died in your first world war, the eleven million who died in your second, the thirty seven million who died in your third. Shall I go on?
So unless the official list of Earth's world wars changed between seasons, the First World War that lasted from 1914 to 1918 in our history had six million fatalities in
Star Trek's history, the Second World War that lasted from 1939 to 1945 in our history had eleven million fatalities in
Star Trek's history, and the Third World War that has not yet happened in our history had thirty seven million fatalities in
Star Trek's history.
Since the fatalities for World War I and World War II are much fewer than in our history,
Star Trek should be in an alternate universe where fewer countries were involved in those wars and/or those wars were much shorter, in order to explain their lower casualties.
Spock's words may imply that Earth had later world wars than the first three, and thus that the Eugenics Wars, listed as Earth's last world war, were World War Four or later. Note that Spock says that thirty seven million died in the Third World War, while he also says that entire populations were bombed out of existence in the Eugenics Wars, implying many more deaths than thirty seven million.
In
Star Trek: First Contact the Enterprise E travels back in time at Earth:
DATA: According to our astrometric readings we're in the mid twenty-first century. From the radioactive isotopes in the atmosphere I would estimate we have arrived approximately ten years after the Third World War.
RIKER: Makes sense. Most of the major cities have been destroyed. There are few governments left. Six hundred million dead. No resistance.
WORF: Captain!
(the Borg sphere is firing at the surface)
PICARD: Mister Worf. Quantum torpedoes.
WORF: Ready, sir.
PICARD: Fire.
(the Borg sphere explodes)
PICARD: They were firing at the surface. Location?
RIKER: Western hemisphere, ...North American continent. At a missile complex in central Montana.
PICARD: A missile complex? ...The date? Mister Data, I need to know the exact date.
DATA: April fourth, two thousand sixty-three.
PICARD: April fourth?
RIKER: The day before First Contact.
DATA: Precisely.
So if April fourth, 2063 in the First Contact calendar (FC) is approximately ten years after the Third World War, the Third World War should have happened about 2053 FC in the First Contact calendar.
Since Spock mentioned:
the thirty seven million who died in your third
[World War] and Riker said that the Third World War resulted in
Six hundred million dead.
it seems logical to deduce that Spock and Riker mentioned two different conflicts. 600,000,000 dead is about 16.2 times 37,000,000 dead.
Therefore, it seems likely that historians renumbered Earth's world wars sometime between the era of TOS and the era of TNG, dropping at least one conflict previously considered to be a world war from the list, so that the new Third World War was previously counted as the Fourth World War, or possibly had an even higher number.
Spock said that the Eugenics Wars were the last of Earth's world wars on his list. Nobody would leave the Third World War mentioned in
Star Trek: First Contact, with six hundred million dead, off the list of world wars used in the TOS era, so the Eugenics Wars could not happen before the Third World War of
Star Trek: First Contact.
Therefore, the Eugenics Wars either happened after the Third World War of
Star Trek: First Contact or else were the Third World War of
Star Trek: First Contact under a different name.
If the Eugenics Wars happened after the Third World War of
Star Trek: First Contact Spock's lists of Earth's world wars would have gone something like this:
First World War roughly equivalent to World War I from AD 1914 to 1918 in our history, but with many fewer fatalities. The world war that seems most likely to have been dropped from the list of world wars in the era of TNG.
Second World War roughly equivalent to World War II from AD 1939 to 1945 in our history, but with many fewer fatalities. Possibly renumbered as the First World War in the era of TNG.
Third World War happening sometime after AD 1945, with thirty seven million dead. Possibly renumbered as the Second World War in the era of TNG.
Fourth World War happening about 2053 FC, with six hundred million dead. Renumbered as the Third World War in the era of TNG.
Fifth World war or Eugenics Wars, happening in the period of about 1993 to 1996 SS, which is sometime after about 2063 FC, with entire populations being bombed out of existence. Presumably renumbered as the Fourth World War in the era of TNG.
If the Eugenics Wars were the Third World War of
Star Trek: First Contact under a different name Spock's lists of Earth's world wars would have gone something like this:
First World War roughly equivalent to World War I from AD 1914 to 1918 in our history, but with many fewer fatalities. The world war that seems most likely to have been dropped from the list of world wars in the era of TNG.
Second World War roughly equivalent to World War II from AD 1939 to 1945 in our history, but with many fewer fatalities. Possibly renumbered as the First World War in the era of TNG.
Third World War happening sometime after AD 1945, with thirty seven million dead. Possibly renumbered as the Second World War in the era of TNG.
Fourth World War or Eugenics wars happening in the period of about 1993 to 1996 SS, which is about 2053 FC, with six hundred million dead, & with entire populations being bombed out of existence. Renumbered as the Third World War in the era of TNG.
Note that the period of about 1993 to 1996 SS (in the "Space Seed" calendar, is roughly equal to about 2053 FC (in the First Contact calendar). If about 2050 to 2056 FC equals about 1993 to 1996 SS, the year one in the "Space Seed" calendar should equal about the year 55 to 62 in the First Contact calendar.
Presumably various religious or ethnic groups would sometimes persuade the United Earth government to replace the then official calendar of the United Earth with the calendar they prefer.
