Chrome sync: is mobile history merged into my desktop’s?

I am trying to save mobile chrome’s browsing history but I heard unless I root my android
phone, I can’t.
So I decided to use Chrome’s sync option.

But the concern is that I don’t want to lose my desktop’s browsing history when I sync my mobile
smartphone’s and then turn the sync option on my desktop for my initial purpose of saving and checking my mobile history.

So is it one way sync or are they merged together safely?
I don’t want to guarantee that nothing is lost when I use this option.