The Military

Background
The military are only encountered throughout the events of Adventure mode and they do not appear in any other mode in the game. As in any other movie or video game, their sole purpose was to be deployed by the United Nations in a struggle to combat the invading aliens attacking Earth.

Typically, not only do they have UFOs on their hands but they must also deal with the epidemic of monsters appearing across every continent of the planet. Their appearances are as follows:

Opening cinematic
CH-53 Sea Stallions are used to lift the top-secret EMP matrix emitters around the planet.

Midtown Park
The military send tanks out to attack Congar after he had been seen chasing down a few police cars down the road (right next to the building of which player 1 would spawn on top of in Versus mode). He rips apart a Mobile Command Unit truck, and the tanks begin to fire shells at Congar, until he unleashes a super sonic roar, which makes the tanks explode as a result (also displaying Congar's special ability).

As soon as Congar has scaled the building he was next to a few seconds earlier, an AH-1 Cobra attack helicopter fires at him, until he throws a radio antenna at it, knocking it out of the sky and causing it to explode. Two CH-47 Chinooks come and both helicopters attempt to restrain Congar with 2 huge cuffs to maintain him.

However, Congar is too powerful and he tugs both cuffs tethered by both helicopters, sending both helicopters flying into the building beneath him, exploding on impact.

Phase 1 - Togera
Togera can be seen raising his foot, and bringing down hard upon a tank, he then grabs another tank, crushing it in his palm. Finally, an attack helicopter attempts to engage combat with Togera, but one of his sharp spikes protruding from his right arm begin to increase in length, he then swings his arm, slicing the helicopter in half, causing it to explode (also displaying Togera's bone-shedding abilities to the player's monster, to show them what they are up against).

Phase 2 - Robo-47
After Togera has been defeated, tanks and missile vehicles can be seen rolling in and attack helicopters are also present, both from the North of the map. Once a few of each unit has been seen coming into the area, Robo-47 will drop down from the sky, causing a shock wave of rubble to fly into the air.

He shall then point to the player's monster and command the military units to attack it (also displaying that the military shall not attack Robo-47, posing an even bigger threat). The tanks shouldn't be much of a problem, but the Cobra gunships can be slightly annoying. The real ground-based threat is the mobile missile launchers. A barrage can easily drain your health by a lot. An easy way to deal with the entire ground force is to activate your crowd-control special attack while cloaked. Or, you could possibly grab one of the launchers, and use it as a gun.

Phase 1 - Giant Ants
As the player's monster is attacking the mutant fire-ants emerging from the large ant hill, the player can wrench off some defense turrets mounted upon the large metal barrier in the North of the map, next to the military bunkers and empty Cobra helicopters. These defense turrets can be used as a gun to hold off incoming mutant fire-ants, and the choppers can be thrown.

Phase 2 - Boss - Goliath Prime
Once the player has defeated the giant ants that are attacking them, Goliath Prime can be seen flying over the large metal fortress, landing on top of the roof just above the large metal doors. Inevitably he was the direct solution for eradicating both the invading UFOs and the monsters rampaging through cities.

He also has the ability to transform, which possibly means that the world's militaries were desperate to handle the outbreak of giant monsters by creating such a sophisticated mecha.

Metro City
A few Cobra attack helicopters can be seen chasing after Preytor, who is also flying past huge skyscrapers. She eventually lands on one of the very tall buildings in the center of the area, dodging the helicopters and swiping at them whilst they could not see her, causing the helicopters to explode.

CH-47 helicopters can be seen carrying a large metal container down a road near the tall buildings, and out of it, Mecha-Congar bursts out and attacks the player's monster. Additional AH-1 Cobras will also be patrolling around large buildings during the fight between Preytor and Mecha-Congar, and they shall shoot any monster upon sight. Oddly, Mecha-Congar will not attempt to kill Preytor. She must really fly quite nicely...

Century Airfield
Two Raptros dragons pull down and destroy a large, twin-engined, propeller-driven aircraft before noticing the player. The appearance of the aircraft suggests that the military was using this airport as a base to strike at the UFOs. The large planes that either are parked or land here have U.S. Air Force markings. They could either be command aircraft, transports, or bombers. The smaller planes are U.S. Navy F4U Corsairs, likely brought from storage after the UFOs destroyed all the world's jet fighters. However, none of the vehicles will attack you, in any game mode.

Bay Town
Tanks can be seen opening fire upon some invading UFOs in the middle of the map, halfway up the city's main thoroughfare. They are seemingly having difficulty fighting against the assault of UFOs, with an entire company of tanks destroyed. Just then, 2 mechas, similar to that of Robo-47 (the 2nd and 3rd alternative skins of Robo-47), drop down onto the map with one fist formed into a giant hammer, smashing the UFOs as they land. After that they notice the player's monster and begin to attack it.

Tsunopolis
Just after 2 mechas, similar to that of Ultra-V (the 2nd and 3rd alternative skins of Ultra-V), land on the map and begin to attack the player's monster, UH-1 gunships can be seen patrolling various parts of the map, and when the player's monster is spotted they will shoot upon sight.

Trivia

 * The weapons on armed vehicles can be used as a ranged attack, by pressing Square. Using a mobile missile launcher in this way can prove useful against Robo-47.
 * The MCU in the first mission has a similar winged emblem to Robo-47.
 * Gambler's Gulch is the only level where ground vehicles will attack the player, and is the only level to feature the mobile missile launcher.
 * All vehicle/turret ammo is limited. Once it runs out, the player can only use them as a thrown weapon.
 * It is unknown how or why the military send out Robo-47 but don't send out the first Ultra-V, considering the fact that Robo-47 was re-awakened by UFO radiation, and Ultra-V went berserk due to the effects of UFO radiation. Also, Robo-47 was a discarded mecha, whereas Ultra-V was specifically designed to combat both the alien invasion and the giant monster outbreak.
 * However, this can be debated. For example, the Robo-47 helping the military in Gambler's Gulch could be a different Robo-47, the additional Robo-47s defending Baytown could be newer versions and the additional Ultra-Vs could also be newer versions.