(idiom) to say what one means or think and act as one; describing a person whose external appearance and inner thoughts coincide

outside appearance and inner reality differ; to say one thing but mean another; to think and act differently

to form an integral part; for the inside and outside to match and complement each other

(literary) describes a place that is naturally protected by mountains and rivers; strategically situated and easy to defend

to act coordinately from within and without; to be in harmony internally and externally

be attacked by the enemy from both inside and outside; facing threats from both within and without

to match inside and out; to be consistent in appearance and reality

The external and internal aspects complement and assist one another.