[Grammar] What does 'it' refer to?

[nininaz]

Hi Teachers,
that could n't be a subject is it right? because that is an object instead of subject ..
What does 'it' refer to? and What is the meaning of the bold context?
when relative pronouns play the role of 'object' how can we recognize them?

"He moved to Paris in 1843 and began writing papers to promote
democracy and to end poverty. He wrote a paper which was so
revolutionary, so challenging to the established political order,that it had to be smuggled back into Germany. "

Thanks.

 

[Raymott]

'That' isn't the subject or object, and it's not a relative pronoun. It's a conjunction.
Do you understand the following sentences:
"How fat was she? She was so fat that she had to go on a diet." Era così grasso che ...
"How hungry was he? He was so hungry that he ate four hamburgers."
The construction is: ... so X that Y ... "così Y che Y"
"The paper was so revolutionary ... that it had to be smuggled back to Germany."

 

[nininaz]

Thanks for your help, I am not familiar with conjuctions
According to what you said , so 'it' refers to paper?

 

[Raymott]

According to what you said,[STRIKE]so[/STRIKE] 'it' refers to paper?

Yes

 

[MikeNewYork]

Yes, "it" refers to "paper".