strategist; tactician; schemer
軍師の献策が戦局を動かした。
The strategist's counsel changed the course of the war.
名軍師と称えられた人物がいた。
There was a figure who was hailed as a brilliant strategist.
軍師は敵の弱点を見抜いていた。
The strategist had seen through the enemy's weakness.