A battle morph, also known as a combat morph, is a morph used predominantly to fight or attack. The Animorphs each acquired morphs specifically for the purpose of fighting the Yeerks and standing against Hork-Bajir warriors. Each morpher for the most part had a primary and secondary battle morph.
"I glanced over at Jake, who'd morphed a sleek, deadly tiger. At Rachel, a massive, towering grizzly bear. Marco, a gorilla with enormous hands and the strength to tear a human apart limb from limb. At Ax and Tobias who'd chosen their own forms. An Andalite whose razor-tipped tail was as lethal as lightning and twice as fast. And a red-tailed hawk with talons created to puncture, rip, and tear."
In The Forgotten, the Animorphs (minus Tobias) acquire jaguars to use as their battle morph while trapped in a rainforest; however, the morph is rendered unusable due to the effects of the Sario Rip.
Andalites do not often use a battle morph, since their own bodies are well-equipped for battle, although Ax has sometimes morphed for battle, such as assuming a rattlesnake and cheetah morph when missions required him to fight in front of humans; Visser Three possessed a variety of morphs that he would use to battle the 'Andalite bandits', but he rarely used any of these morphs more than once and showed no sign of a specific favorite.
Although not listed above, many of the battle morphs are shared amongst the Animorphs. For example, all of them possess polar bear and Hork-Bajir morphs. Rachel, Cassie, Tobias, and Ax also have elephant morphs while Marco and Jake have a rhinoceros morph; Jake, Cassie, Marco and Rachel also all have wolf morphs. However, Cassie is the only member of the main Animorphs to lack a unique battle morph of her own. In The Hidden, she acquires a buffalo, and in The Unexpected, she acquires a kangaroo, but is never shown using them again after the events of these books.
The Animorphs in their various battle morphs fighting a Howler.
The Animorphs in their battle morphs.
The five human members of the Animorphs, with their human form juxtaposed with one of their main battle morphs: Rachel-Bear, Marco-Cobra, Tobias-Hawk,Cassie-Wolf, and Jake-Tiger. From the inside cover of Back to Before.