Dummy it

It's yet another dummy/anticipatory. The meaning is "To protect you is my duty". Postponing the subject and putting "it" at the front in its place is a common pattern in English. You have seen numerous examples in your reading.

park sang joonHow about "The thing is my duty that I protect you"?

No.

Thank you, GPY, for your so very helpful answer.

I don't yet know what "dummy it" means.
I was wondering what I should

The "it" in "dummy it" refers to nothing.

http://grammar.about.com/od/d/g/Dummy-It.htm

http://www.ucl.ac.uk/internet-grammar/minor/antit.htm

park sang joonI don't yet know what "dummy it" means.

Dummy "it" is when you cannot meaningfully replace "it" with a noun. For example, "It rained today". Some people class the anticipatory "it" as a type of dummy "it". You can replace anticipatory "it" with a noun (or something functioning as a noun), but you have to adjust the rest of the sentence too.

park sang joonI don't yet know what "dummy it" means.

It doesn't mean anything.

park sang joonI was wondering what I should call "it" which refers to nothing.

You have been given two terms. I'll give you a third one: a formal subject. This term, translated into your own language, may occur in English grammar books written by

park sang joonI don't yet know what "dummy it" means.

English sentences require a grammatical subject. When no noun is appropriate, the pronoun "it" is used as a placeholder.

park sang joonI was wondering how I can interpret #1 in the view of non-native English speaker.

To protect you ..... > To protect you It ........ > It
is ......................... > ... is ...........\................ > is
my duty. .............. > ... my duty. .....\.............> my duty
............................