The Evolutionary War (Japanese: ハンテールとサクラビス！進化の謎！ Huntail and Gorebyss! The Evolution Mystery!) is the 3rd episode of Pokémon: Advanced Battle.
The gang goes to the ABC Islands. They should first go to A Island (the one with the Pokémon Center). They spot Wailmer swimming nearby. Suddenly, they also see a group of children riding some Water Pokémon - Gorebyss and Huntail. Brock tells them that they both evolve from Gorebyss and Huntail. A boy bashes a girl, but they still continue. They spot more boys and girls bashing - they want to come first on the island. Team Rocket see the gang going, but their submarine is stuck between rocks. They work hard to get going, but the submarine gets flooded.
The gang arrives to the Pokémon Center. Joy receives a call from a woman - her Corsola got cold. She sends Corsola to Joy via the teleporter. The gang is amazed by that innovation. Suddenly, they hear a boy and a girl arguing - about which Pokémon is stronger: Gorebyss or Huntail. Joy calms them down - she is the teacher as well as a nurse. Nurse Joy tells them that kids from islands B and C became rivals. Also, she mentions that Clamperl who live around become Gorebyss at island B and Huntail at island C. Because of that, the people always argue who is better. The children ask a man which Pokémon is better. The man is no other but Prof. Birch.
Prof. Birch comes to the gang, greeting them ans says he is here to study Clamperl's evolution. Nurse Joy proposes Birch should give some lecture to the children. A girl asks how Clamperl evolves, so May tells him that on island B Clamperl evolves into Gorebyss and on Island C into Huntail. Birch tells them that Clamperl evolves into Huntail a deep sea tooth is needed, while into Gorebyss a deep sea scale is required instead. He shows them a replica of the tooth and the scale. Before they go, a girl comes to lead them to Island C.
The girl tells them when they come into a cave (the one they are in), Clamperl evolves to Huntail. Birch tastes the water, realizing it is full of minerals. He takes a sample to study. A boy appears to study his "enemy", although the girl wants him to go away. Birch proposes that he will be the Island B guide. The boy shows them a cave and if Clamperl is put to the water, it turns into Gorebyss. Birch tastes the water - it is similar to the water on Island C, so he also takes a sample. The girl appears to study her "enemy", but soon departs.
At the Pokémon Center, Birch studies the water. Nancy (the girl) and Keith (the boy) appear to learn what Birch studied. They want their Pokémon to evolve into Gorebyss and Huntail. They send both their Clamperl, so Nancy wants a Gorebyss and Keith a Huntail. Team Rocket spies, so Meowth decides to steal Huntail and Gorebyss for boss, to give it for his "wild side". Birch learned that the water from Island B contains particles of deep sea scale, while on Island C deep sea tooth. Team Rocket appear and release the net to capture the Pokémon. Ash sends Corphish who cuts the net. Jessie sends Seviper to bite, but the attack is deflected due to Harden. Corphish uses Crabhammer, hurting Seviper. James sends Cacnea and uses Pin Missile, but the Clamperl's shells close, negating the attack.
Seviper goes to use Poison Tail, but due to BubbleBeam, the attack is cancelled. Clamperl use Water Gun, pushing Cacnea and Seviper. Pikachu uses Thunderbolt, blasting them off. The gang returns to Island B, checking the cave. Keith found a deep sea scale and gives it to Nancy. Nancy places the scale onto Clamperl, but nothing happens. Birch proposes to send Clamperl to Pokémon Center, so she does it. They go to Island C - Nancy finds a deep sea tooth. She gives it to Keith, who gets Clamperl out and places the tooth on it. Clamperl does not evolve, so Keith sends his Clamperl to Pokémon Center, per Birch's advice.
At the Pokémon Center, Joy gives them the Pokémon. They send the Clamperl out, along with the deep sea scale and tooth. Nothing happened during their travels, but suddenly, they evolve! Brock tells them it is not a stone that makes them evolve quickly. May proposes to take them to waters, so Nancy and Keith do that. Team Rocket appear once more, but in a Kingler machine. Gorebyss uses Agility and Huntail bites. Ash sends Grovyle and attacks with Bullet Seed, but with no effect. Huntail and Gorebyss use Water Pulse, pushing the machine. Meowth releases a hand, but both Pokémon dodge. The second hand releases a net, capturing them.
Grovyle cuts the net with Leaf Blade, setting them free. Gorebyss uses Confusion, levitating them and Pikachu uses with Thunder. Huntail uses Screech, blasting them off. Joy comes to tell them the ferry started working, so the gang leaves, waving goodbye to Birch and Joy. Nancy and Keith ride their Pokémon, telling the gang that the people from the islands began to get along when they showed their Pokémon. The gang leaves them to go to next island.
- Featured Pokémon: Mudkip, Treecko, Torchic
- The rocks on each of the A-B-C Islands resemble some katakana characters: The A island seems to have an I (イ), the B island has a Ro (ロ) while the C island has a Ha (ハ). Iroha is a Japanese poem that's also a perfect pangram, useful in learning the basic syllables much like an abecedarian. The translation from Iroha to A-B-C would be acceptable, as it preserves the original idea.
- The dub title is a reference to the Revolutionary War.
- While telling Ash and his friends about the evolution of Clamperl, Professor Birch shows them an example of a DeepSeaTooth, which is same color as a DeepSeaScale.
- Huntail and Gorebyss were in the water when Pikachu fired Thunderbolt at Team Rocket's Magikarp submarine and should have also gotten electrocuted since water conducts electricity.
- In the final attack before Team Rocket blasts off, Huntail uses Screech, and then Pikachu uses Thunder. In the dub, Pikachu attacks first, and it is Huntail who makes them blast off, despite Screech not being a physical move. This is an example of anime physics.