grammar - Difference between [Noun]する vs [Noun]をする vs [Noun]だ

I've never really understand the difference between these 3 structures :

ものすごいスピードで攻撃したのですが...

ものすごいスピードでの攻撃をしたのですが...

ものすごいスピードでの攻撃だったのですが...

I wouldn't be surprised if the first 2 were totaly interchangeable, but what about the third? Does it have a particular nuance or is it virtually the same as the others?

Answer

It is mostly just different ways of saying the same thing. In english the difference might be something like this:

1. (subject) attacked with an amazing speed.

When the noun signifying the action (攻撃)　is directly tied with the verb する, you can interpret the compound as a verb. ie. "attacked".

2. (subject) made/performed an attack with an amazing speed.

In normal usage these ways of saying the sentence is as you say interchangeable. Grammatically you disconnect the noun signifying the action from the verb する, thus you "do an attack" instead of just "attacking".

3. It was an attack with an amazing speed.

Here, since you end the sentence with だ/だった　instead of する, you've moved from "doing" to "being", hence "It was".

Hope that answers your question.