ISA Marines

The Interplanetary Strategic Alliance Marine Corps is the ground component of the ISA Navy. The ISA Navy transports the Marines to and from their theaters of operation and supports them when they are on the ground. Each of the ISA Navy's Cruisers can carry 7,500 personnel, 5000 of whom could be ISA Marines and the rest crew and support personnel. It is possible however that a smaller contingent of marines are assigned to ships, with additional troop numbers made up by other troops such as legionnaires or regular troops.

History
The Marines were first deployed by the UCA against Helghast forces in the First Extrasolar War. Now, they are powerful and well-supplied military force.

The Second Extrasolar War
When the Vektans called upon Earth to provide it with reinforcements after the Helghast invasion, Earth answered with a large naval task force being loaned to the ISA Navy; as usual, this task force carried its own complement of Marines. Unfortunately, the Helghast was able to destroy 2 UCN vessels as they arrived over Vekta with the SD platform before the rest of the Earth Fleet got ambushed by Helghast cruisers, eventually leading to the destruction of Vekta's only chance of being liberated, by the end of October 2357, the entire Earth fleet was destroyed leaving only one to escape back to Monastary.

After Vekta fell, most of the ISA forces that managed to escape the planet retreated to Monastary, where multiple failed counter attacks were launched against Vekta, in a desperate attempt to reclaim the planet, but failed.

ISA launched a retaliatory attack against the Helghast's home planet of Helghan, with the Marines at the forefront of this invasion. Arriving approximately two weeks before the second wave, the first ISA assault wave took heavy casualties, but succeeded establishing several planetary beachheads.

After the arrival of the second wave, which notably included a few Special Forces units, including multiple UCA forces, the attack resumed in earnest.

After intense fighting in both cramped urban and dangerous desert wasteland conditions, the ISA forces steadily gained control of vital territories in and around Helghan's capital city, Phyrrus, including the city of Thyrious.

However, the Helghast unleashed a devastating surprise counterattack that destroyed most of the ISA's orbiting atmospheric command fleet, including the ISA's flagship.

In addition, the commanding officer for the entire Helghan campaign, Colonel Jan Templar, is killed in the surprise attack by Helghast Colonel Radec himself.

With mounting losses and a drastically reduced support structure, the ISA's forces were nearly annihilated when General Lente launched a ground offensive against the ISA Ground forces from the center of Pyrrhus; with most of the remaining ISA forces concentrated in the city, this was a severely crippling blow, to the ISA's only chance in conquering the Helghast capital.

Marines are the first to fight on the battlefield and are known for their honor, valor, bravery and most importantly, their dedication as the main military forces of the ISA. Ironically, with their vaunted reputation as being one of the ISA's finest ground units, they found that the Helghast were more than a match for them, especially on the Helghast's home turf.

It was only the arrival of a Naval Legionnaire contingent-Alpha Squad itself- that helped turned the tide on Helghan, despite the Invasion failing, due to the interference of both Radec's battalion and General Lente's Third Helghan Army.

6 months after the invasion, the ISA since retreated off of Helghan, upon launching a defensive strategy, against the Helghast, where they returned to Runekara, where these weakened military personal were then ordered by Earth to remain.

Battle Dress Uniform (BDU)
In on field engagements, the Marines are commonly issued with black Combat helmets resembling 21st century Ops-Core helmets, equipped with orange protective lenses, to protect from shrapnel, integrated communications systems and mountings for equipment such as Night-vision Goggles. The Marines are typically issued with body armor resembling plate carriers and MOLLE vests, but some Marines prefer to remove them for increased mobility and decreased weight. They are also commonly issued backpacks, for storage of equipment, ammunition carriers attached to their belts, and black combat boots.

The Marines under the command of Alex Grey wear a similar uniform with minor differences such as the lack of protective lenses and their faces are covered with balaclavas.

Weaponry
ISA Marines are equipped with a variety of different weaponry. The standard-issue weapon of the average grunt would be the M82 Assault Rifle, with the underslung M303 Grenade Launcher issued for extra firepower if needed. The Marines also field several revolvers as part of its arsenal, with powerful M3 and M4 Revolvers being the most popular choice of sidearms. For suppressive fire, the M224-A1 Light Machine Gun is used to increase the firepower of squads currently on the battlefield, for use on vehicles and as an emplacement for base defense. Special forces teams and scouting parties are typically issued the suppressed M66-SD Submachine Gun. The LS13 Shotgun is commonly fielded for close-quarters engagements.

Infantry teams were also issued the M80 Missile Launcher for greater firepower against fortifications and buildings, and as anti-armor support against tanks and armored vehicles.

Vehicles
For reconnaissance and anti-infantry support, the Corps field the Jeep, often equipped with mounted versions of the M22-A1 LMG. For armored infantry transport and seaborne engagements, the tracked ISA AAPC was used.

For heavier engagements, the ISA Archer Tank and LS209 Exoskeleton were both fielded for anti-aircraft and anti-tank roles, respectively. For ground support, the ISA Lancer was used for indirect and direct artillery.

The cheap and reliable Intruder was also fielded for infantry transport and close-range firepower, though years later this dropship was superseded by the ISA VTOL.

Identified Formations

 * 6th Marine Division
 * 8th Infantry
 * 32nd M.A.T.
 * Convoy Avenger
 * Convoy Punisher
 * Convoy Nemesis

Trivia

 * Garza turns out to be friends with one Marine, Jeffries, who is assumed KIA after his Intruder is shot down in the Corinth River stage. He is most likely either the soldier who is executed in front of Sev or he is the soldier who Garza grieves over before leaving the area. It may imply that Garza had served with Jeffries previously, or maybe even that Garza has some history within the ISA Marine Corps before joining the Legion special forces Alpha Squad.
 * The ISA Marine Corps rank structure and equipment is mostly based on the real-life United States Marine Corps.