A commander-in-chief or supreme commander (often used in historical or military contexts).
戦国時代の有力な主将が戦を指揮した。
A powerful commander of the Warring States period led the battle.
主将として軍を率いる責任は重い。
The responsibility of leading the troops as commander-in-chief is heavy.
The captain of a team (in sports); the leader who unites the team.
サッカー部の主将に選ばれて、彼は責任感が強くなった。
He was chosen as the soccer team's captain and became more responsible.
主将は試合後にチームを代表して挨拶した。
The captain gave a speech on behalf of the team after the match.
彼女は主将として練習の方針を決めた。
She decided the practice policies as the team captain.