The game begins when Green Town is attacked by the Tan army, and Sarge is battling through the war torn city killing Tan Spotters and APCs to save the Town. When the battle is over, Sarge is informed by Colonel Grimm that the Tan Army surrendered and that there would be a peace ceremony later that night, but there is also a rogue army that had stolen some army men infantry moulds and can now build an army led by Lord Malice. Sarge's mission is to find and terminate Malice, as well as to track a missing squad already sent. Sarge arrives in the area (a beach) and battles his way through until he reaches the Tan portal and destroys some Tan ammo trucks.
Then, he finds plans indicating that there is a bomb attack planned for the peace ceremony which is where Plastro, Colonel Grimm, the heroes, and a battalion of Green Army men are located. He is also contacted by Lord Malice who tells him that the bomb is in the peace statue and that he can't wait to see Sarge's face as his squad is incinerated before his eyes. Sarge charges through the portal to stop the ceremony but he is too late. His entire squad as well as Green Town and the Green Army Battalion have been destroyed. Contrary to popular belief, the entire Green Army was not decimated in the explosion; in fact, Sarge comes across several Green Army squads who help him along the way. However, Sarge will fight the Tan alone. He then sets out to kill Malice.
Cheats
All weapons Pause the game, then hold L and press Right, X(2), Y, X. If you entered the code correctly, a message will appear. Note: Only weapons normally available in the current level will be unlocked.
Invisible mode Pause the game, then hold L and press Up, Left, Right, Up, X. If you entered the code correctly, a message will appear.
Slow-motion mode Pause the game, then hold L and press Left, Down, Up, Right, X. If you entered the code correctly, a message will appear.
Fish eye camera Pause the game, then hold L and press Left, Up, Right, Down, X. If you entered the code correctly, a message will appear.
Beagle holes, footprints, and burns Pause the game, then hold L and press Down, Up, X, Y, X. If you entered the code correctly, a message will appear.
Alternate fade Pause the game, then hold L and press Right, Up(2), Down, X. If you entered the code correctly, a message will appear.
Alternate lighting Pause the game, then hold L and press Up, Right, Up, Down, X. If you entered the code correctly, a message will appear.