Quadruped Fortress

The Quadruped Fortress is a powerful and gigantic Ravager battle machine resembling an immense crawling Hector that operates as a mobile battle station and carrier. They have served as major foes throughout the series' campaigns.

2017
The Quadruped Fortress first appears off the coast of Japan, being deployed from the Mothership itself in mission 14: Fortress. In the next mission, Blockade, the EDF attempts to take it down, but is unsuccessful. The Fortress then continues its path of destruction, destroying a large part of Tokyo. In mission 33: Surprise it is discovered that the Fortress is dormant, either refuelling or undergoing repairs, and the EDF sends a strike team to destroy it before it reactivates; they fail, and the Fortress escapes. They try one last time in mission 34: Breach after coming up with a plan to attack its underside, and after a long battle the machine finally falls.

It is mentioned there are three more in Shanghai controlling a force of Hectors in mission 29: Assault, implying they are some kind of control station or relay in the Ravager command network.

Armament and strategy
The Quadruped Fortress is enormously large, well over 100 metres tall and 200 metres long, and possesses miniature shield screen generators which protect it against all attacks from the front and partially from the sides; these are impenetrable even to weapons that would normally go through targets, just like a regular shield screen. Unlike in 2017, these shields are always visible, rather than fading out if they have not been hit recently. Its four feet produce massive eruptions of debris with every footstep, and it destroys any building it touches with its legs, with the footfalls doing huge damage to anything even near them; just avoiding the foot itself is not enough to avoid damage. As well as this, the Fortress has a rapid-fire rotary projectile launcher and five powerful laser turrets. On its back are two giant plasma cannons, though these are never directly aimed at anything and are not a factor in battles with it.

Being a carrier as well as a moving fortress, it is able to deploy various enemy types, using a transport bay on its underside hidden behind two large doors that open downwards to reveal the glowing interior. In missions where the Fortress can be destroyed this is the only part of the Fortress that will damage the machine itself, though it has other locations that can be attacked.

Since the weak point is high up, mobile and spawns enemies while active, it can be very difficult to effectively target; long-range, flat-trajectory weapons such as sniper rifles are most effective since they do not require the player character to fire from directly under the Fortress. It can be particularly tricky for an Air Raider to attack a Walking Fortress since their vehicles have limited gun elevation; aiming an Epsilon Armored Railgun diagonally up from one side of the Fortress is most effective, though it will be destroyed in short order if the laser turrets on that side are still active.

A Quadruped Fortress follows a fixed path and will not deviate from it to chase Storm Team, content to simply attack them in passing.

In both of these games, any fight with a Quadruped Fortress has three possible phases, which are either cycled by scripting or damage; in the first, the Fortress simply walks around firing its plasma cannons at nothing in particular and dropping off the first type of enemy it can deploy, usually Ants.

In phase 2 it will start firing the rotary projectile launcher mounted on the rear of the main hull, and switch what type of enemy it drops, usually to Flying Drones or later Flight Vehicles. This weapon continuously fires explosive projectiles at anything in the Fortress' rear arc, and can be destroyed separately to the Fortress itself.

In phase 3 it will start firing its laser turrets and generally switch to dropping Hectors or Blue Hectors. The laser turrets are extremely dangerous, doing constant damage and slowing down anything they hit, easily able to pin a Wing Diver in place, though other classes can escape being pinned by rolling or dashing. There are five turrets, two on the front of the main body, two to the rear, and one between the rear set of legs. Like the rotary gun, these can be destroyed individually, though they cannot receive damage until they become active. They can also fire through the Fortress' shields.

Appearances
Quadruped Fortresses are first mentioned in mission 14: Preventing Landfall, where it is revealed that they are being dropped all over the world by the Ravager Motherships as part of their invasion. Following this, Storm Team first faces off against one of these fearsome enemies in mission 16: Fortress Siege, but the EDF is well prepared after the 2017 invasion, so much so that EDF forces in Great Britain have already destroyed the Fortress attacking there. While Storm Team fights a holding action, the Air Force launches their secret weapon, a powerful bomb known as the Grind Buster, annihilating the Walking Fortress within a few strikes. This Fortress cycles through its drop phases, variously dropping Hectors and Flying Drones, and starts out in phase 1 in 2025 and phase 2 in 4.1. When the Tactics Officer calls in that Grind Buster is locked on, the Fortress apparently hears her and jumps to phase 3; it is a good idea not to be anywhere near it when this happens.

However, this is not the only such vehicle, and later Storm Team faces another without the assistance of the Air Force. First encountered in mission 48 (50 in 4.1) Fortress Frenzy, it is initially impossible to defeat and switches phases regardless of whether or not it has taken damage. Storm Team fights a holding action to allow civilians ahead of it to be evacuated, and are ordered to disengage when this is accomplished. This Fortress alternates between dropping Ants, Crimson Ants, Flying Drones and Hectors.

The final showdown with the Quadruped Fortress is mission 62 (65 in 4.1) Fortress Attack, where Storm Team must destroy the Fortress unassisted. Here, it cycles its enemy drops forward as it takes damage, going from Ants to Flight Vehicles to Blue Hectors as it takes progressively more damage.

It is mentioned during mission 66 (70 in 4.1) Teeth of the Universe that during a battle in America the Moving Fortress X-4 succeeded in destroying several Quadruped Fortresses with its Linear Cannon before ultimately being defeated by the massive new Ravager battleship, the Argo. This is the last mention of them in 2025.

In 4.1 a final Quadruped Fortress is added to mission 87 (83 in the original game) Massive Mobilization. This Fortress starts the mission inactive and when aggro'd walks in a semicircle and then stops completely. It only deploys Flight Vehicles, and is partially destroyed with a single Grind Buster strike, leaving Storm Team to finish it off. The Grind Buster strike instantly switches it to phase 3.

Quadruped Fortresses also appear in DLC, with perhaps the most extreme example being the mission God's Army, which features three of them and an Argo, though one is immediately destroyed by a Grind Buster strike when the mission begins.

Trivia

 * While it is said to be the largest and strongest Ravager land weapon, in 2025 and 4.1 it later turns out to have lost this crown to the even larger Argo.
 * In 2025, it is possible to land on the Quadruped Fortress while using a Wing Diver. Hiding in its knee joints can provide some protection from the cannons, and it is even possible to fly inside the hatch while it is closing, though as with transport ships, the weak point cannot take damage while it is closed.
 * The large cannons on its back are never aimed at anything, though they deal enormous damage if the player character is caught in the blast in EDF 2025 and 4.1; it is a fixed 2,000 damage hit regardless of difficulty level, though the cannon blasts tend to overlap and deal 4,000. Being hit is only really possible if the player character is a Wing Diver or an Air Raider using a Helicopter and deliberately flies up into them, though.
 * Fortress Siege unhelpfully instructs the player to attack the Fortress' invincible legs in the mission briefing for both 2025 and 4.1. Oddly, this does not do a lot.
 * The mission descriptions for Fortress Frenzy and Fortress Attack are partially reversed in both EDF 2025 and 4.1, with the former suggesting the player is supposed to be trying to destroy the Fortress and the latter suggesting they are trying to redirect it.
 * While players of EDF 4.1 might consider using Walking Fortress Balam to even things up a little, this will only reveal just how large the Quadruped Fortress is. Oddly enough, punching the Quadruped Fortress in the shins does little to deter it.
 * In 2025 the Fortress' turrets would continue firing after it was destroyed if they had not been taken out, making the wreck very dangerous. This no longer happens in 4.1.