In contrast to the peaceful human colonists of Naboo, the native Gungans are a proud warrior species. The amphibians have long maintained a huge standing army -- the Gungan Grand Army -- as one of their proudest traditions. The martial nature of the Gungans has caused tension between the natives and the Naboo for centuries.
The Gungans prefer technology that is harmonious with the ecology of their world. Their weaponry is no different. The Gungan Grand Army uses domesticated animals for transport -- Gungan scouts ride swift-footed kaadu into combat, while hardy falumpasets and fambaas haul heavy weapons and shield generators into place. Gungans use the exotic, energetic plasma mined from Naboo's crust not only to power their cities, but also as ammunition for their weapons.
Naboo's unique geology has left vast caverns of uncharted oceans filled with dangerous creatures. The Gungan army is equipped to defend against such threats from the deep. They have harnessed the energetic plasma found in the planet's depths to become their power source, and for use in weapons.
Boss Nass was so impressed with Jar Jar Binks' ability to bring the Gungan and Naboo people together, that he promoted Jar Jar to the rank of general. The jittery Jar Jar was one of the commanders of the Grand Army during the Trade Federation invasion of Naboo.
To draw the Trade Federation battle droid army out of the city of Theed, the Gungan Grand Army gathered in the grass plains nearby.
When Mon Cala fell to Separatist attack, the Jedi Council could not equip a clone army for reinforcements in time. They turned instead to the Gungans, who rushed the Gungan Grand Army into battle.