Fortress Siege is the sixteenth mission in Earth Defense Force 2025 and Earth Defense Force 4.1: The Shadow of New Despair. It is the first gameplay encounter with the Quadruped Fortress and introduces Bomber Midnight and its Grind Buster superweapon. It also introduces mission briefings that are dangerously incorrect, and is the first mission with a non-standard win condition.
Note: all screenshots are from 4.1, and so the Fortress' positions will not match the 2025 description.
Objective[]
2025: The Ravagers have begun a serious offensive. They've begun simultaneous attacks in several areas, and they're using a giant walking fortress, 200 meters long. It is formidable, with weapons bristling on its gigantic frame. The attack aircraft Midnight has been dispatched to destroy it. We are to attack the fortress' legs, and then defeat any remaining enemy forces. Ground forces, head out!
4.1: The Ravagers have begun a serious offensive, attacking several areas simultaneously. Here, they seem to be utilizing a giant walking fortress, bristling with weapons that's roughly 200 meters in length. The attack aircraft Midnight has been dispatched to destroy it, but we are to aid them by taking out the fortress' legs, then eliminating any remaining enemies. Ground forces, move out!
Storyline[]
The "defense lines" that were talked about in the last mission are revealed to be "three squads of Rangers and Storm Team standing on a walkway" as the mission begins with the mighty Quadruped Fortress looming in the distance. The Rangers seem as skeptical about this as anyone, with one shouting "It's too huge!" and another declaring they cannot defeat it with only ground troops.
HQ cuts in, rather unhelpfully telling the EDF ground troops to destroy it with air raids. As the Fortress begins to drop its first wave, the Rangers declare that "Hectors are coming out of the Quadruped Fortress!" HQ, for ones sorting out air support by himself rather than waiting for the Tactics Officer to do it, announces that Bomber Midnight is on its way to deliver a strike with a new penetrating "bullet," Grind Buster.
An EDF soldier successfully identifies Flying Drones deploying from the Fortress as it lumbers on, then Aurora Situation Report chimes in. She exposits that the other Quadruped Fortresses are approaching major cities, while the EDF has constructed defense lines (one can only hope the others involved more actual construction) and is intercepting them. One Fortress has apparently already been destroyed on the "isle of Great Britain," she says, and praises the EDF for putting up a good fight against such an overwhelming enemy. The Tactics Officer, sounding like she just ran in and sat down, quickly says that Drones are being deployed from the Quadruped Fortress as the second wave of them are dumped out and collide with each other tactically.
HQ, finally remembering to tell the ground troops to do something they can actually do, orders the Rangers and Storm Team to "clean up all enemies besides the Quadruped Fortress."
As much buffing and polishing commences, the Tactics Officer announces that Midnight will arrive in the combat area momentarily, and shortly afterwards HQ orders the troops to destroy the new group of Hectors dropping from the Fortress. Since Midnight seems to be taking its time, the Tactics Officer then announces it will arrive momentarily again, and HQ decides the situation warrants a double negative, saying "there is nothing that Grind Buster can't penetrate" and the EDF forces just need to wait a little longer. He then orders the EDF troops to "destroy the Flying Drones" as the Fortress drops its last wave.
The Tactics Officer declares, with appropriate drama, that "Midnight has acquired the target." Unfortunately the Quadruped Fortress seems to hear this and decides now is the time to switch all of its guns on. This proves unhelpful at dealing with the strategic bomber which is about to kill it, and shortly afterwards the Tactics Officer gives the order "commence air raid!" and confirms the Grind Buster has been fired. The Fortress is bombarded with Grind Busters and explodes as she declares "Impact!" toppling over where it stands. She confirms "Defeated target!"
All is not well though, as she immediately states that the EDF has confirmed an "incredible number" of Hectors elsewhere. HQ decides this is the "main unit," and with obvious glee adds "Buuuutttt...We still have armored forces stashed away" as if he is talking about hiding a bottle of whiskey in the filing cabinet.
The Tactics Officer informs him there is a dispatch request to the Air Force, but HQ is in full dramatic mode and ignores her, declaring "The battle on the ground is beginning!" Which is presumably different to it "finally beginning" or the fight starting now.
4.1 Changes[]
"You could, you know, not park directly in front of it? Guys?"
4.1 starts the mission off in a different area, some distance back from the starting location of the original mission among the skyscrapers, where the 2025 Fortress deployed the final wave of Drones. A rather poorly thought-out attack is made on the Fortress by two E551 Gigantus tanks and an E651 Titan, with the driver announcing "Big fortress, better tank" followed by completely missing it with the vehicle's Requiem Cannon. He then calls for the tanks to retreat, which they do by...reversing about a block, and then parking up still in the path of the Fortress. This stupid behaviour is rewarded with the Fortress standing on the Titan and Gigantuses shortly afterwards and instantly destroying all of them (they must not have been well); the non-recruitable NPC Ranger Squad added here does not last long either. Because the Fortress uses its rear rotary turret to mop up the EDF units from this starting "scene," it is always active during the mission rather than only coming on at the end.
Since the Gigantus tanks continue firing until they are destroyed (unlike the Titan, which only fires one shot) they will usually succeed in seriously damaging one of the first group of Hectors.
Following this the Quadruped Fortress walks forward to just past the park, circles around to the side of the park, walks across it, back into the city again, turns around at the other end of the park, walks back across it, and is destroyed while trying to walk back into the city.
The NPC group in the park is still present, but only one group is up on the walkway; the other two are in the circular area immediately behind it.
On the more useful side of things, the Quadruped Fortress' turrets will no longer continue firing after it is destroyed in this version.
Enemies[]
Both versions:
Quadruped Fortress (invincible but turrets can be destroyed if active)
Two waves of Hectors, all with 1 x Particle Gatling Gun and 1 x Spark Launcher, 4 and 7
Three waves of Flying Drones, 22, 33, 40
Online Limits[]
Armor Limit
There's no limit for Inferno difficulty.
| Difficulty | Ranger & Air Raider | Wing Diver | Fencer | |||
| 2025 | 4.1 | 2025 | 4.1 | 2025 | 4.1 | |
| Easy & Normal | 577 | 570 | 338 | 335 | 721 | 712 |
| Hard | 1741 | 1809 | 920 | 954 | 2176 | 2262 |
| Hardest | 3160 | 3732 | 1630 | 1916 | 3950 | 4665 |
Weapon Level Limit
| Game | Easy & Normal | Hard | Hardest | Inferno |
| 2025 | 6 | 29 | 54 | 91 |
| 4.1 | 5 | 29 | 56 | 91 |
Approximate Weapon Drop Rate
| Game | Easy | Normal | Hard | Hardest | Inferno |
| 2025 | 0-2 | 0-3 | 12-26 | 0-49 | 0-58 |
| 4.1 | 0-3 | 0-4 | 12-24 | 0-50 | 0-58 |
Strategy[]
2025[]
To begin with, the mission description is bizarrely misleading; it is impossible to damage the Quadruped Fortress' legs in any way. Quite why this is in both mission descriptions is a mystery.
This is actually a survival mission; Bomber Midnight will destroy the Quadruped Fortress after it has deployed five waves of enemies, and all Storm Team has to do is last until this has happened. The mission will end shortly after the Fortress is downed even if there are still enemies remaining; indeed, it will give a "cleared" message even if all of the players present are downed, as long as at least one was up when the victory conditions were fulfilled. It is thus possible (if unrewarding, in multiple senses) to beat this level without killing a single enemy.
Since the enemies present are Drones and Hectors, some thought is required for armament as these two are fought in totally different ways and unlike Preventing Landfall the NPCs are not equipped to take on the Drones by themselves.
For a Ranger, the best combination is one of the Emerald multi-missile launchers and a powerful rocket launcher like a Goliath (Air Tortoise can do the trick on lower difficulties) or a heavy sniper rifle for dealing with the Hectors. A decent assault rifle or shotgun can also be useful against the Drones since they are deployed quite densely.
For a Wing Diver, there are plenty of options among her homing launchers to deal with the Drones with a Mirage being ideal, though a Thunder Bow is also good against them. The Hectors are her main problem; Plasma Launchers take quite some time to kill them, and there are eleven of them in this mission with only Rangers with assault rifles to help out. Her only real options are to pick away at them at long range with a sniper weapon or Plasma Launcher, or fight them at dangerously close range with something like an Idunn. The confident may wish to try their luck approaching them from above and using a Rapier; while this is short-ranged, it will defeat a Hector extremely quickly, and good energy management will allow a group to be taken down, though there is the risk of a lucky Spark Launcher hit while approaching.
The Ravagers were not prepared for the Ranger Special Indifference Unit.
For an Air Raider, the player should determine which enemy they want to deal with using their vehicle, and bring equipment to deal with the other. A BM03 Vegalta is best for dealing with the Drones and some Vegalta variants such as Heavy Cannon can also put the hurt on the Hectors depending on the level, while an Epsilon Armored Railgun is ideal for the Hectors but its machine guns will not be very good for taking out the drones. If going the first route, it is best to bring a powerful anti-armour Strike like the Artillery Team's Cannon or one of Whale's 120mm Cannon strikes and the most powerful Limpet Gun the player has or C Bombs to lay in the path of the Hectors (since they will lumber towards the Air Raider's position, their path is quite predictable), while the second will benefit from bringing ZE-Guns and a Skytrap Wire gun if the player has one. To prevent the guns from harming NPCs, it is a good idea to place them on the pedestals at intervals along the wall to the side of the park, as shown above-right. This is generally a good trick for an Air Raider to remember on this map.
The Fencer has plenty of options for dealing with the enemies; the Hectors can be defeated with a good Blasthole Spear if the player has mastered Dash-cancelling, though it is a good idea to bring a Hand Cannon or Gallic Heavy Cannon in the other pair to soften them up first. High Altitude Impact Missiles can soften up the Drones but are not really a good idea unless the Fencer retreats to deploy them since the Drones are deployed close by, and it is generally better to use a Hand Gatling, Dexter Automatic Shotgun or one of the back-mounted rapid-fire Galleon Cannons against the Drones here.
The Quadruped Fortress itself is not a target, but it is a threat. The primary problem during the mission is the Fortress' feet; every time it takes a step it creates a powerful hit which is functionally an explosion, causing damage in the area indicated by a pillar of kicked-up dirt, which is rather larger than the Fortress' actual foot. Like an explosion, it will knock characters off their feet.
The two doors in the underside of its "torso" section open when it is deploying enemies, also revealing a flat glowing red panel similar to the core of a Transport Ship. This will later be the Fortress' weak point, but as with the Transport Ships in The Return and Day of the Demons, shooting the core here produces damage effects but no actual damage.
An EDF Ranger squad leader arrests an Air Raider for suspiciously staring at the Quadruped Fortress' shield screens.
While it is not necessary to shoot at it, it is worth noting a few other aspects; the huge translucent glowing orange "visor" and the two similar sections under the backs of its dorsal cannons are shield screens. These forcefields are indestructible and block all projectile attacks, even those that would normally pass through multiple enemies.
The Fortress has two weapons which will actually be relevant in battles with it; the first is a rotary cannon mounted on the back of the main "torso" section of the vehicle's body, which will shoot a constant hail of explosive projectiles at anything which is in its rear diagonals, though its fire is obstructed directly behind except at very close range by the vehicle's own hip section. This only normally comes into play late in the fight when the Tactics Officer says Midnight has locked on; it is on when it has glowing red bands around the base of the ball mounting and the cannons. It will, however, turn on earlier if the Fortress' weak point is attacked. It is worth noting the orange shield screens on the Fortress' sides do not block fire from its own weapons. The cannon turret can be destroyed, and it does not have an enormous amount of health either. Doing a fair amount of damage will make it temporarily stop firing, but it is not destroyed unless it explodes.
The second weapon is five powerful spherical laser turrets, four on the underside of the "torso" section with one at each diagonal, and one between the rear pair of legs. These come on only when it is announced that Midnight has acquired it, and are on when they are glowing red. These have limited range; moving away from the Fortress when it is deploying the third wave of Drones will avoid damage from them, though they can be destroyed once they become active if the player feels so inclined. The front pair are hard to take out since they are protected from most angles by either the front "visor" shield screen or the Fortress' front legs, and also have the best arc of fire. They fire repeated red laser beams which hit rapidly and can stunlock a Wing Diver in mid-air, which is often fatal since all she can do is fall slowly.
While the fire from its giant dorsal plasma cannons might look frightening, this is never aimed at anything and the only way to be hit by it is to deliberately fly into it with a Wing Diver or Helicopter. If the player for some reason decides to do this, the shots deal a fixed 2,000 damage regardless of difficulty, but since they have a blast area that overlaps, being hit by anything but the outer edge of the shot will probably deal 4,000.
The mission starts with the Quadruped Fortress directly ahead. It will walk over part of the platform Storm Team starts out on, so it is a good idea to recruit the three Ranger teams here and then retreat. It turns away to the left rather than walking right on through the Rangers. As it is moving forward, it will deploy four Hectors one after another from its underside hatch: two end up in front of the starting position and two to the left.
It then wanders off into the city behind the park, destroying every building it touches along the way and deploying the first wave of Drones as it goes. It will then briefly stop moving entirely, and deploy the second wave of drones when it starts again. Its path loops back into the park, and as it walks across the far end it will drop seven Hectors in slow succession. As it stomps back though the city it deploys a final very large group of Drones, and then the Tactics Officer will say the magic words "Midnight has acquired the target."
"Gad, something I haven't destroyed! Begone, puny human, this is my calling!"
The Fortress will respond by going absolutely ape and turning on all of its weapons at once, which as noted above is best addressed by being nowhere near it when this happens. One minute and 30 seconds later the Grind Buster is fired and the Fortress destroyed, though if the guns on its left side (including the one between the rear legs) are still active the wreck will keep firing until the mission ends. As soon as the Tactics Officer mentions a large force of Hectors the win condition has been triggered and the mission is all over bar the shouting.
4.1[]
"IT'S NOT DIFFERENT AT ALL, IS IT STEVE?!"
As before, the Fortress begins walking straight towards the starting location; while it is tempting to stick around near the three tanks to fight the first group of Hectors, this is unlikely to end with anything but taking a lot of damage when the Fortress stomps through the area. It is better to make a break for the park area and deal with the Hectors away from the Fortress.
The Fortress in this version spends a lot more of its time in the park, which means clearer lines of fire, though it also means clearer lines of fire for the Drones. The Fortress seems to deploy the second group of Hectors closer together than before making them a little more dangerous: this is probably because it is turning slowly rather than walking straight forwards when it drops them in this version.
Tactics and weapon choices are essentially the same. It is if anything a slightly easier mission in this version.
| 1-10 | Reconvene • Spreading Disaster • Winged War Goddess • Setting Sun • Wind Break • Underground Cave • Eruption • Retaliation • Beach Fear • The Return |
| 11-20 | Air Force • Day of the Demons • Takedown • Preventing Landfall • Land Collapse • Fortress Siege • Valley Shadows • Artillery • Breaking Through • Shining Stronghold |
| 21-30 | Into the Depths • A Trap • Giant Robots • Summit Ship • Anchored • Silver City • Crimson • High-Speed • Bloody Mountain • Brute Force |
| 31-40 | Charge Phase 1 • Charge Phase 2 • Dark Prisoner • Charge Phase 3 • Thunder • Infiltration • Convergence • Inferno • Starship • Dense |
| 41-50 | Crossing • Search • Waterside Bugs • Annihilation • Natural Calamity • Steel Beast • Void Ship • Blue Fighters • Earth Defenders • Fleet Attack |
| 51-60 | Mountain Pass Trap • Fortress Frenzy • Pincer • Ravages of War • Air Mobilization • Bug Invasion • Transport Ship Surprise Attack • Bug King • Crazy Skies • The Fleet Below |
| 61-70 | Bad Premonition • City of Horror • Mountains Ablaze • Breaking Through (2) • Bug Tower • Fortress Attack • Mountain Liberation • Sniper Attack • Mountain Giants • Towering Beast |
| 71-80 | Teeth of the Universe • Giant Ship • Spearhead • Tower Siege • Den of Thieves • Death Queen • Machine Squad • Monster Party • Labyrinth of Light • City Flaws |
| 81-90 | Monster Camp • Fallen Flagship • Heaven's Army • Encircling • Divine • The Threat • Troubled Valley • Battle to the Death • Massive Mobilization • Legion of Monsters |
| 91-94 | Scorching • Demon Army • Surrounded! • Star Eaters |
| DLC 1: Special Forces | Exploration • Giant's Advance • Silver Camp • Citadel • Floating Fleet |
| DLC 2: Mutant Rampage | Advance • Mountain Assault • Enemy Camp Infiltration • Underground Advance • Giant Robots • Battle Species • Beast Mountain • Dark Arena • Gathering Around • Armored Species • Iron Wall • Mountain of Change • Whirlwind of Death • Bugged City • The Tough • Golden Darkness • True King • Final Impact • Into Destruction • Ship of Dragons |
| DLC 3: Beyond Despair | Tracking • Underground Complex • Blocked Pass • Close Formation • Dragon Ship Fleet • Heavy Artillery • Bloody River • Dangerous Goldmines • Beast Mobilization • Total Protection • Aerial Bombing • King of Armor • Cannon Defenders • Traps Behind • Four Kings of Nightmares • Resistance Against the Twilight • Shivering Nexus • Three Giants • Crimson Lotus • Starry Prison |
| 1-10 | Reconvene • Spreading Disaster • Winged War Goddess • Setting Sun • Wind Shear • Underground Cave • Eruption • Retaliation • Beach Fear • The Return |
| 11-20 | Air Force • Day of the Demons • Takedown • Preventing Landfall • Land Collapse • Fortress Siege • Valley Shadows • Artillery • Breaking Through • Shining Stronghold |
| 21-30 | Into the Depths • A Trap • Giant Robots • Summit Ship • Anchored • Silver City • Crimson • Assault • High-Speed • Bloody Mountain |
| 31-40 | Brute Force • Charge Phase 1 • Charge Phase 2 • Dark Prisoner • Charge Phase 3 • Thunder • Infiltration • Convergence • Inferno • Starship |
| 41-50 | High Density • Dozing Beast • Crossing • Search • Waterside Bugs • Annihilation • Natural Calamity • Steel Beast • Void Ship • Blue Fighters |
| 51-60 | Earth Defenders • Fleet Attack • Mountain Pass Trap • Fortress Frenzy • Pincer • Ravages of War • Crash • Air Mobilization • Bug Invasion • Transport Ship Surprise Attack |
| 61-70 | Bug King • Crazy Skies • The Fleet Below • Ill Omen • City of Horror • Mountains Ablaze • Breaking Through (2) • Bug Tower • Fortress Attack • Mountain Liberation |
| 71-80 | Battle of Giants • Sniper Attack • Mountain Giants • Towering Beast • Teeth of the Universe • Giant Ship • Spearhead • Tower Siege • Den of Thieves • Death Queen |
| 81-90 | Machine Squad • Monster Party • Labyrinth of Light • City Flaws • Monster Camp • Fallen Flagship • Heaven's Army • Encircling • Divine • The Threat |
| 91-98 | Troubled Valley • Battle to the Death • Massive Mobilization • Legion of Monsters • Scorching • Demon Army • Surrounded! • Star Eaters |
| DLC 1: Time of the Mutants | Air Offensive • Giants Advance • Recon • Dust Town • Defense Line • Underground Advance • War Breed • Mountain Assault • Enemy Camp Infiltration • Dark Arena • Beast Mountain • God's Army • The Gathering • Armored Species • Iron Wall • Silver Base • Shifting Mountain • Whirlwind of Death • Bugged City • Toughness • Golden Darkness • True Sovereign • Final Impact • Floating Fleet • Into Destruction • Ship of Dragons |
| DLC 2: Extreme Battle | Tracking Bogeys • Underground Complex • Blocked Pass • Close Formation • Dragon Ship Fleet • Heavy Artillery • Overflight • Dangerous Goldmines • Beast Mobilization • Total Protection • Bombs Away • King of Armor • Cannon Defenders • Bloody River • Three Giants • Traps from Behind • The Four Horsemen • Cross the Line • Facing Off • Crimson Lotus • Shivering Nexus • Last Bastion • Starry Prison |