In Pokémon Ruby and Sapphire, what battle format first put two Pokémon on each side?

Pokémon Ruby and Sapphire first introduced Double Battles, in which two Pokémon fight on each side.

The games debuted in Japan in late 2002 and internationally in 2003 as the third generation of the main series. Double Battles changed the familiar one-on-one format by placing two Pokémon from each trainer on the battlefield at the same time.

This format made move targeting and team coordination much more important. Some attacks could affect multiple combatants, while abilities, weather, and positioning created combinations that were less important in ordinary single battles. Ruby and Sapphire also introduced Pokémon Abilities and Natures, which gave individual Pokémon additional strategic traits.

Double Battles are distinct from later formats. Triple Battles, which placed three Pokémon on each side, arrived in Pokémon Black and White. Rotation Battles also debuted in that generation, while Max Raid Battles appeared much later in Pokémon Sword and Shield. Double Battles remain a recurring format in the franchise and are central to several official competitive rulesets.