In the Royal Canadian Navy, capitaine de frégate is the official French language name for the rank of commander.
The NATO rank code is OF-4, the official translation for instance of the German Fregattenkapitän as well as the French capitaine de frégate into English is "commander senior grade".
The Russian/Soviet equivalent is "captain of the 2nd rank" (капитан 2-го ранга)
Insignia of a capitaine de frégate in the French Navy
Insignia of a capitaine de frégate in the French Navy
Insignia of a capitano di fregata in the Italian Navy
Likewise, when I was a frigate captain later on, if an “adversary” minehunter came to escort me I would have increased to 30 knots before you could say “childish, but effective” ... included frigates.