Translation:This event led to a crisis between two countries.
The word neden is actually the Ablative case of the pronoun ne = "what?". You've probably encountered this word already here on DL, as a word for "why", along with niçin and niye.
It might make more sense to you now, to realise that when you're asking "why?" in Turkish, using neden, you're literally asking “from what?”, “(out) of what?” something happened.
Now, when something causes something else to happen or, in other words, leads to it, it is the…reason, the cause, the grounds of it! As the usual case in Turkish is, there’s an Arabic synonym for it: sebep.
A very common expression in Turkish containing the word neden is “bu nedenle”, literally “with this reason”. It means “for this reason”, “that’s why”, “therefore”, “consequently”, “thus”. Similarly, using the synonym sebep, we have “bu sebeple” and “bu sebepten dolayı”.
As for "neden olmak", it's a compound verb. There are quite a lot of compound verbs in Turkish, formed by a noun along with an auxiliary verb, such as etmek, yapmak and olmak — the first two meaning to do / to make and the third one is the verb to be / to become. In order to say “to cause sth”, you’d have to use the syntax “-e neden olmak” or “-e sebep olmak”, literally "to become the reason / the cause towards sth":
- Aşırı hız ve alkol kazaya neden oldu., or
- Aşırı hız ve alkol kazaya sebep oldu.
A similar way of saying that, would be by using the expression “-e yol açmak”, literally “to open the way towards” which translates into “to lead to sth”:
- Aşırı hız ve alkol kazaya yol açtı.
The examples, by the way, have the exact same meaning: “High speed and alcohol caused (or led to) the / an accident”.
Hope this helps :)
I don't mind learning new expressions, but happening upon them as if you were supposed to already know them ("strengthen...") is immensely frustrating, since it makes you feel like a moron ("now why in heavens can't I make sense of this sentence?" - "oh, because I've never been told the sense of this construction"...)