Battle Zone consists of three phases: skirmish; battle; and battle leader, and can be triggered in free roam by vanquishing multiple enemies. Upon reaching a certain amount of vanquishes, the text "PROVOKED ENEMY FORCES" will appear and some enemies will then spawn. Defeating these spawned enemies will cause the message "A SKIRMISH HAS ERUPTED" to appear and the skirmish phase will begin. On this phase, the player needs to vanquish either a Champion enemy hero or a boss (referred to as a battle skirmisher in-game) that is marked on the HUD in order to proceed. There is an invisible 4-minute time limit to vanquish the skirmisher, otherwise the skirmish dissipates and the Battle Zone fails.
Upon vanquishing the skirmisher, the battle phase begins. The player needs to vanquish a certain amount of enemies within a 4-minute time limit, which is displayed on the HUD, otherwise the battle dissipates and fails. Near the end of this phase, the player can make an educated guess as to which battle leader will be spawned by looking at the enemy spawn patterns when the enemy forces are almost depleted. Unusual spawn patterns that hint the forthcoming battle leader include an excessive amount of spawns of a particular character class; characters with certain customizations or Champions that normally don't spawn anywhere else. They are:
- Spooky Squash: Kernel Corns with the "Jack-O-Corn" hat and Squash. There will always be a single Squash if Spooky Squash is the Battle Leader. If the Squash is destroyed, a new one will spawn.
- Giga Torchwood: Snapdragons
- Super Bean: Citrons
- Sunflower Queen: Sunflowers
- Hypno Sunflower Queen: Champion Hypno-shrooms and Night Caps
- Sproutrage: Peashooters
- Lucy: Champion Hypno-shrooms and Night Caps
- Flotsamuel: Peashooters
- Teddy: Chompers
- Bluehorn Corn: Kernel Corns
- Pinky Rain: Snapdragons
- No-Neck Raffi: Cacti
- Bam-Bam-Boo: Weeds and Peashooters
- Sherman: Acorns with the "Picnic Warrior" hat.
- Pollen Kate: Sunflowers
- Queen Capra: Roses
- Pound Cake: Hypno-shrooms and Night Caps
- Zen Sensei: Foot Soldiers with the "Jungle Warrior" hat and non-Champion Zen Sensei
- Baron von Bats: 80s Action Heroes with "The Finisher" costume, Champion Foot Soldiers with the "Corporal Shootypants" costume, and Scientists with the "Mad Batty" hat
- Yeti Zombie: Yeti Imps, All-Stars, and Champion Scientists with the "Maroon Buffoon" costume
- Just Brad: Foot Soldiers
- The Advertiser: Champion TV Heads
- Sgt. Plaid Attitude: Foot Soldiers and Heal Zombies
- Captain Cozplay: Imps
- Charnado: Super Brainzes
- Shadez 2 Cool: 80s Action Heroes
- Rolleeta: Electric Slides
- Cap'n Sharklunch: Captain Deadbeards
- Woofzy: All-Stars
- Red Janet: Space Cadets
- Dr. Spork: Scientists
- Basecoat Bert: Engineers
Once the enemy forces are depleted, the battle leader will spawn and the player needs to vanquish them within another 4-minute time limit in order to complete the Battle Zone. Battle leaders from a character class will almost always have one or more special abilities that are unattainable normally, such as a greatly increased damage output of their weapon, the ability to heal and turn enemies invincible, or being able to use a certain ability faster than it is normally allowed, while boss battle leaders have a much higher health than the regular ones.
There is a bug where vanquishing the provoked enemies will not trigger the skirmish phase. What causes this bug is unknown, but usually vanquishing some more enemies will provoke the enemy forces once again and this should usually allow the player to start the skirmish phase normally.