Godzilla 2: War of the Monsters is a turn-based strategy game, in which the player must defend cities and other important locations from Godzilla and other monsters. Godzilla, Mothra, Baragon, Hedora, Rodan, other monsters, and even the occasional UFOs make appearances in different combinations throughout the levels.
Each level begins with a prescribed number of military units that can be moved around the map on a grid. Sometimes units can be "ordered" out of military bases, but this involves a very limited number of units and is more like queuing up initial units rather than actual choosing of what units would be best. These units can be ground- or air-based, ranging from tanks and fighter jets to special weapons that can be unlocked with research. Special weapons include a freeze ray, or even a "top secret" jet that must be assembled from pieces. In later levels, some of the monsters even become allies in the fight against Godzilla and company.
Combat involves moving units adjacent to enemies and attacking them, which enters the combat screen and uses a kind of random "slot machine" luck system. Once an attack is selected, the slot machine of three icons can be engaged by pressing controller buttons - if luck (or really good timing) allows for matching symbols to be selected, then the attack has higher chance of hitting or a greater damage output.
The same music plays throughout the game, with one track used during the player's turn and another during the monsters' phase.