Question

Which battle was fought in the most northern region?

Answer 1

Assuming that you're talking about the Pacific War.

The battle that was fought in the most northern region would be the Autelian Island Campaign. The war zone was located on the northern part of the Pacific area

Answer 2

The battle that was fought in the most northern region would be the Autelian Island Campaign. The war zone was located on the northern part of the Pacific area