Which Assassin's Creed game introduced the naval battles later expanded in Black Flag?

Assassin's Creed III introduced the naval battles that were later expanded in Assassin's Creed IV: Black Flag.

The naval sections of Assassin's Creed III let players command the warship Aquila in missions along the Atlantic coast. The game combined sailing, wind direction, cannon fire, boarding actions, and ship upgrades, giving the series a new gameplay style alongside its land-based stealth and parkour.

Assassin's Creed III is set largely during the American Revolution. Its main protagonist is Ratonhnhaké:ton, also known as Connor, a Kanien'kehá:ka Assassin. The naval missions are separate from the game's primary frontier and city environments but became one of its most distinctive additions.

Black Flag built on this system and made maritime exploration a central feature, with Edward Kenway sailing the Jackdaw throughout the Caribbean. Rogue also emphasized naval gameplay, but Assassin's Creed III was the main series entry that introduced it.