On Articles in English: Definite, Indefinite, and Zero
To declare war on something is an instance of zero-article marking in English, which is triggered by any of several circumstances. It’s like how there may be three schools in your town, but when you speak of your children being at school, no article should be used. These three all mean slightly different things:
- My kids are at school.
- My kids are at the school.
- My kids are at a school.
Zero-article usage varies in between different regional dialects of English. In the United States, one normally speaks of going to the hospital or going to the university (but not going to college, oddly enough), while just a few miles north of the Canadian border spoken by people with no discernible accent difference from the first set, you will often as not find those particular articles dropped.
You can also see variation in article choice between individual speakers from the same region, or even the same speaker in different utterances.
- I want to grow up to be president.
I’m now president / I’m now the president.
I’m boss around these here parts, and don’t you forget it.
- I’m the new boss around here.
I’m afraid your question is too broad to be wholly answered in the Stack Exchange Q&A format, because it is subtle, somewhat complex and quirky, and because native speakers themselves are seldom aware of the actual “rules” under which they are operating.
The best way, really the only way, to pick up this sort of thing is by constant exposure to the quirks of usage displayed by native speakers themselves. After all, that’s how they learned it themselves.
Getting the knack of knowing when to use or not use articles can be especially difficult for English language learners. As I’m about to show, this can happen even when coming from a language closely allied to English. for those coming from languages with no articles at all, it can be a complete mystery altogether.
However, just because two different languages have articles doesn’t mean they use them the same way. This is easily observed when comparing article usage in English versus in a neighboring language from the Germanic or Romance families. Those language do have articles, but just what triggers or suppresses article use is quite often a bit different from how it works in English.
In Romance, for example, when you declare what profession you’re in, you don’t use an article.
- English: I’m a teacher.
- Spanish: Soy profesora.
Similarly for where you’re from, etc.
- English: I’m a Quebecker.
- French: Je suis Québécois.
Or JFK’s famous gaff where due to his accidental word-for-word translation into German, he came off sounding like a bismark:
- English: I’m a Berliner.
- German: Ich bin Berliner.
So even coming from neighboring languages, it’s hard for English language learners to always get it right.
That’s partly because of their native proclivities, but partly because of the variation within English itself, as occurs here with your case of war: with some words, the article is possible but not obligatory, and dropping it changes the meaning a bit.
As with your war case, sometimes more than one way of phrasing it is possible, such as how the line from the famous song “La Bamba” can translate from having no articles in Spanish into noun phrases with articles in English:
- Spanish: Yo no soy marinero, soy capitán:
- English¹: I’m not a sailor, I’m the captain.
That’s a good example because it allows for an alternate, zero-article translation as well:
- English²: I’m no sailor, I’m captain.
Understanding the difference may lie at the heart of what is bothering you with war versus the war. There in the song, leaving out the article in the version English makes the noun a more abstract thing, which is just what is going on with your war situation. (Technically, the no there also functions as a determiner, which is what an article is, too.)
You point out war as being a count noun. This is true in some situations and not in others. When one observes that Germany and France had three wars in the space of three-quarters of a century (1870–1945), or when one speaks of “the war to end all wars”, one is clearly thinking of war as a discrete thing, something countable and separate.
However, when one speaks of going to war, being at war, in open war, making war upon another, or a reason for war, it is not the same notion because it is no longer talking about one or another individual instance. It has been made into a condition, a state of being.
Being in a state of war is like (well, syntactically) being in a state of bliss: it takes no article, being used now as an abstract noun not a discrete one.