In the Nara and Heian Eras the Most Militarized Region

In the Nara and Heian eras the most militarized region of Japan was the

A) western region exposed to attacks by Filipino pirates.
B) eastern region,which were the staging ground for campaigns against tribal peoples in the north.
C) southern region closest to Korea.
D) northern region,which were the staging ground for campaigns against tribal peoples in the north.