The sentence as quoted is not entirely unproblematic. As other answers show, its structure is not immediately clear to at least some native speakers, although others find the meaning obvious. I fall in the latter group and understand exactly what the sentence means and how it’s structured, but though I don’t consider it to be ungrammatical or unclear, I don’t find it very idiomatic.
The real issue is that it tries to combine two features of English syntax in a way that strains them almost to breaking point. Those features are interrogative fronting and catenative constructions.
In English, interrogative phrases (that is, a cluster of words beginning with a question word like what, which, how, etc.) can appear in two different locations: either in their underlying position (subject position, object position, etc.) or fronted, that is, moved to the beginning of the clause.
In main clauses, both are possible (though there is a difference in meaning); when fronting in a main clause, subject-auxiliary inversion applies. So the following are both perfectly grammatical:
She went where? / Where did she go?
In subordinate clauses, however, fronting is mandatory (
* means ‘ungrammatical’):
*I know [she went where] / I know [where she went]
In “no matter how hard she decided to try to quit smoking, she would never succeed”, the main clause is “she would never succeed”, and the rest is a subordinate clause, which means that the interrogative [no matter] how hard must be fronted and put at the beginning of the clause – as indeed it is.
Many languages, including English, make it possible to string multiple verbs together like links in a ‘chain’. This is called a catenative construction (from Latin catena ‘chain’). Not all verbs allow for this sort of chaining in English; those that do are called catenative verbs.
The first verb in a catenative construction is the main verb – if the context calls for a finite verb form, it will be the first one. The rest are all in the infinitive (with or without to) or gerund form, depending on the preceding verb – each verb has its own rules.
Most catenative constructions consist of only two verbs, but it is in theory possible to keep going and going, like this:
I decided [finite] to avoid [infinitive] going [gerund] there to help [infinitive] Jim try [infinitive] to pack [infinitive] all his things.
Combining the two
When you have a catenative construction, and one of the chained verbs has a complement which is an interrogative phrase, the same rules of fronting apply:
You want to go where? / Where do you want to go?
(*I know [you want to go where]) / I know [where you want to go]
In the un-fronted example, where appears right after the verb it’s related to: go. The question asks where to go, not where to want, and the position of the interrogative makes this clear.
When fronted, however, the interrogative does not appear near either verb, so it’s inherently ambiguous which verb it belongs with. We require semantic clues to figure out what makes sense:
How fast do you want to go? ← You want [to go how fast]?
How badly do you want to go? ← You [want how badly] to go?
Clearly in the first instance, you don’t ‘want fast’, and in the second, you don’t ‘go badly’ – you ‘go fast’ and ‘want badly’, nothing else makes sense.
As mentioned, most catenative constructions are just two verbs like this, and it’s usually clear which verb the interrogative relates to. But it can become truly ambiguous if you use an interrogative that can fit either verb:
How quickly did he begin to talk?
Am I asking how quickly he began? Or how quickly he talked once he began?
When you add more verbs to the chain, such ambiguities can become even more pronounced, and that’s where things start to break down. Let’s use our previous long example and add some adverbs:
I decided to avoid going there [to voluntarily help] Jim try to pack all his things.
I decided [to stubbornly avoid] going there to help Jim try to pack all his things.
Now what happens if we turn those into a how-question with fronting? Well, the interrogative goes all the way to the front, so suddenly there’s nothing but ambiguity:
How voluntarily/stubbornly did I decide to avoid going there to help Jim try to pack all his things?
There’s just no way of knowing which verbs either of those two adverbs was intended to modify anymore: did I voluntarily or stubbornly decide, avoid, go or help – or did Jim voluntarily or stubbornly try or pack? Most of those make at least some sense, so it’s a complete guessing game.
Lacking any clear way to pinpoint a specific verb, we just sort of give up and decide that it modifies the first verb, ’cause that’s closest. If that doesn’t work, we might try with the last verb instead, which sort of ‘wraps up’ the whole chain of verbs and is usually the most semantically salient one. If there are too many verbs, though, we lose track because there’s too much to backtrack through, so this second strategy only works if the list of verbs is fairly short.
In the quote above, the first strategy works, because you can decide something both voluntarily and stubbornly; but it won’t always be the case that either strategy works, and then you can end up with sentences that become awkward or downright impossible.
Deciding hard to try hard to quit smoking hard
In your example, you have a chain of three verbs – one more than is most common, but not enough that everything becomes a hot mess like my example above. Then you have an interrogative phrase with an adverb that doesn’t really work with the first verb, works excellently with the second, and doesn’t work at all with the third: deciding hard is perhaps not impossible, but it is odd; trying hard is very normal; and quitting smoking hard is quite impossible.
So yours is an intermediate case: the two obvious strategies don’t work, but there’s only one verb left, and that’s a good fit. The structure must be this (
__ denotes the trace in the underlying position;
ᵢ denotes index identity):
She decided [to try hard] to quit smoking → [No matter how hard]ᵢ she decided to try [__]ᵢ to quit smoking
Apparently, this divides native speakers:
- some give up when the obvious strategies don’t work and conclude that the adverb must modify the first verb, but this doesn’t work, so the sentence doesn’t work.
- others go one step further and try with the third, middle verb as well, and finding a match they conclude that the sentence works.
But even if we belong to the second group, having to go to such lengths to correctly place the adverb puts a strain on our cognitive skills – we’re not used to having to work that hard to parse sentences. This irks our brain, and the result is that the sentence still doesn’t feel quite right.
It works, but it’s too much hard work to get it to work, so we find it awkward.