身在曹营心在汉 – shen1 zai4 cao2 ying2 xin1 zai4 han4
Literal translation = body – at – Cao (name) – camp – heart – at – Han (name)
Idiomatic translation = Your body is in the camp of Cao but your heart is in Han’s camp.
This is a very nice Ancient Chinese Proverb. If you can use it correctly it will really touch the hearts of Chinese people and they will be highly impressed with your Chinese.
Cao was a famous war general and appears in the famous book The Three Kingdoms. I haven’t read the book myself but I know the other famous general in there is Zhu Ge Liang and I assume there is one named “Han” as well.
I am not sure if there is a specific story about a certain soldier whom this idiom applies to or not, but it basically comes the history of Caocao and his wars at the time of the The 3 Kindgoms.
The usage and meaning of this is quite specific. I used to think it just meant someone who is there in body but not in spirit (perhaps day dreaming) but the real meaning is about where someone’s loyalty lies.
For example, a company is bought out by a bigger company and maybe fires the managers and a new manager comes in. You still have the same job but now you have a new boss, however you still love the old boss and have devotion to him or her. So although your body is working for the new company and new management, you miss the old company and management and still have loyalty to them even begrudgingly continuing your job.
Therefore, there aren’t many opportunities to use this idiom as it’s meaning is quite specific.