"No more Hiroshima" or "No more Hiroshimas". Some say the former and some say the latter. I'm wondering which is grammatically correct.
The latter is correct. If the meaning is essentially There should or must never be any additional uses of nuclear bombs on cities or against people, as occurred in Hiroshima (and in Nagasaki) in August, 1945, it must be No more Hiroshimas.
People who use this expression are likely using Hiroshima to stand for the bombings of both cities. Hiroshima then, would be conceptualized as a single event, and like the word event, Hiroshima is countable.
No more Hiroshima would usually mean that the city no longer exists. It might also be used in an abbreviated way to express something like We are no longer in Hiroshima (having, for example, travelled out of it from inside it; thanks to JdeBP--see comments), or to express something like I/we/somebody will have no more experience of Hiroshima; for example, because we've left it and won't return.
English learners can perhaps more easily understand the grammar if we consider that "Hiroshimas" refers to Hiroshima plus one or more imagined or theorized cities like Hiroshima (cities that might be attacked with a nuclear bomb like Hiroshima (and Nagasaki) and that might suffer the massive loss and agony that followed. No more events (like that one). As usual, we make the countable noun (Hiroshima) plural by adding s.
It is not surprising that you may see errors in the form *(no) more + [city name/singular noun] because we would rarely see city names in plural form. We normally have in mind one Tokyo, one San Francisco, etc.
It is also likely common to find mistakes in that grammar pattern because more often determines something about quantity of mass or of a noun treated grammatically as mass: We would say no more rice much more often than no more rices.
No more SOMETHING! means:
- you deny someone access to that something.
- you are sick and tired of something and express your feeling of denial.
- you express the fact that something is gone (or you are parting ways with it).
No more SOMETHINGS! means:
- you are against SOMETHING and express your opinion that such thing shouldn't happen anymore.
To explain it in terms of terminology:
"No more Hiroshima" would treat Hiroshima as an uncountable noun. There was five square kilometres of Hiroshima before the nuclear attack, but then there's zero square kilometres of Hiroshima after the attack.
"No more Hiroshimas" would treat Hiroshima as a countable noun. There is one nuclear attack, two nuclear attacks, but hopefully no more nuclear attacks.
It's like saying "I like kangaroo" (which'd be indicate a liking of the uncountable noun of kangaroo meat), versus "I like kangaroos" (which'd indicate a liking of the countable noun of the animals themselves).
As one slight complicating factor, pluralising a city feels a little weird. Maybe they chose not to do it, even if they ought to.
I'd say both are valid. In either case, we aren't literally talking about the city of Hiroshima, rather, what happened at Hiroshima.
We use the noun Hiroshima to mean the destruction of a city with a nuclear weapon. This is a metonym.
I'm guessing that someone who makes either statement is saying that they don't want to see another city subjected to a nuclear attack. In that case, you would say, "No more Hiroshimas." You use the plural because "more" calls for a plural, and you are using the word "Hiroshima" as shorthand for "the nuclear attack that caused massive destruction of the city of Hiroshima". Suppose instead of this shorthand we used a literal phrase, like "nuclear attack". Then I think it's clear you would say, "No more nuclear attacks", plural, not "No more nuclear attack", singular, because "more" calls for a plural. You could recast the sentence to call for a singular, like, "I hope there is not another nuclear attack", or "I hope there is not another Hiroshima".
Someone might say "no more Hiroshima" if what he was trying to say was that the city no longer existed. Like, "After the bomb dropped, there was no more Hiroshima." But I'm guessing that's not the intent.
There is no direct plural in Japanese, so "Hiroshima" is like "sheep." It can refer to one Hiroshima, or it can refer to many Hiroshima.
However, in colloquial usage, we just tack an "s" on for plural in English--otherwise you end up with the very dangerous confusion included in the other questions.
Additionally, since the phrase refers not to the city as such but an event which occurred there (and only one other place), it can be considered to be a new "English" word.
In the end, "No more Hiroshima disasters" would cleanly avoid the problem, though it does lack the enthusiasm of the protest era that the original phrasing intends to load in there.