The meaning of "If Only"
Sentence
If only the calm and restraint of the old city were the face of Yemen.

Question
What's the meaning of "if only"? and is there any synonym?

Thanks for your explanation.

"If only" is a type of wish, a desire. 

 In this sentence: "If only I had a brain" from the movie "The Wizard of Oz", he is wishing that he had a brain. It's a fancy way of saying that you want something.