Complex sentence: The French Navy does not use the term "destroyer"; thus, some large ships of the first rank (like Horizon) are named "frigates", though they are registered as destroyers (with hull numbers "Dxxx").
Split into simpler sentences: The French Navy does not use the term "destroyer" in vessel names. Instead, surface combatants of the first rank (such as "Horizon") are named "frigates", though they are registered as destroyers (with hull numbers "Dxxx").