Does “entscheiden” require the construction “dazu …, etw./jdn. zu tun”?

Question

Wenn ich mich nicht dazu entschieden hätte, dich zu operieren, wärst du auf ewig ein Krüppel.

I just started learning German a couple of days ago, and I’m not sure if I correctly understand the function of the "dazu" here.

I find it interesting to see that the phrase "decide to operate you" in English needs to take a dual form in German (in a manner of speaking), translating into something like:

decide to/for/about that (i.e. to operate you)

The "dazu" seems to have a supplementary role for the comma-enclosed part "dich zu operieren". I wonder if the same goes for "be capable of doing" = "dazu fähig sein, etw zu tun", for instance?

Answer 1

It doesn't need to take a double argument. In fact, both complements are optional:

Ich habe mich dazu entschieden, zu operieren. = I've decided to operate.

Ich habe mich entschieden, zu operieren. = I've decided to operate.

Ich habe mich dazu entschieden. = I've decided to do it.

(The referent of dazu has to be supplied by context.)

Ich habe mich entschieden. = I've made my decision.

(No indication is being given what the turnout was, merely that there is one.)

Instead of the prepositional adverb, a full prepositional phrase can be used:

Ich habe mich zu einer Operation entschieden. = I've decided to perform an operation.

The only thing you cannot do is to combine a full PP with a verbal complement:

*Ich habe mich zu einer Operation entschieden, zu operieren.

This isn't allowed, since it would be either pleonastic or contradictory.

(By the way, "fähig sein" works exactly the same way.)