Multiple approaches are known but all are inexplicably hostile to humans. However, they only have a limited number of tricks in their arsenal.
Their 'breeding' cycle involves infecting metallic objects or ores to spawn new machines. They can infect a building and slowly, but steadily, replace the entire structure with murderous facsimiles. The same buildings later can be armed and put on tracks, turning them into massive siege weapons.
Machine Army collects and recycles organic matters, and it sometimes uses its victims as parts of mechanisms.
The Machine Army lays traps for people by becoming buildings, or more accurately, becoming facsimiles of buildings, in attempt to lure people inside. Until a target enters, the machines remain dormant, but when individuals wander into the trap they will activate and kill the intruders.
In one known example, they replaced a functioning supermarket left devastated by Gold Morning. Repairs were made to the inside, such that it would be more attractive to scavengers and other people who might happen upon it.
A big part of why the Machine Army is so difficult to deal with is because they have developed inter-dimensional technology. The Machine Army compresses itself into interdimensional pockets, that will pop open and continue to spread if they are attacked.
The PRT had locked down Eagleton and patrols regularly, putting some of their more difficult members there. They preferred putting capes there who would blast anything at the first sign of trouble. The organization explored several options on how to deal with the threat, such as nuclear weapons, much like they did with Nilbog.
↑ 1.01.1Cities that break from this convention but nonetheless have departments are named with special designations. [...] Quarantine Sites: [...] Eagleton - Q3 - Site evacuated after Machine Army event, specialized patrols - PRT Master Reference
↑Here and there, deep in the craters and crevices, the ‘trick’ missiles had delivered payloads that weren’t explosive. They looked like veins of metal in rock. In weeks and months, they would ‘hatch’, revealing the machinery that had built itself within. For now, they were paved over. [...] The machines weren’t too challenging to destroy. Dot’s groups had sometimes destroyed them. The trick was that they set in roots wherever they went. Each time they reached a new place, they would keep emerging from that place, from walls and floor and rock and tree. It took care and attention to get the machine out of each of those things, and while that care was being taken, machines elsewhere would emerge, march, and make inroads along the flanks. - Excerpt from Interlude 3 II
↑ 4.04.1She could see the green lights appearing in the background of the display, flicking on one by one, apparently at random. [...] Dot moved closer to the ground to get a look. It was important to know just how far gone this building was.
The entire area behind the fridges was gone. Green flashing lights, wires, computers and metal twisted into shapes that helped it to provide a framework. Machines were working slowly and steadily to refine and develop things. [...] Green lights here and there went dark, the machines hibernating. Dot deemed herself safe to move. - Excerpt from Interlude 3 II
↑He was surrounded, he noted, by the machines. Big, small, utility, weapon. The biggest were house-sized, mounted on treads like those of a tank, each containing a different weapon that they revealed when they unfolded. - Excerpt from Radiation 18.z
↑There was a machine that was as tall as a house, with spindle legs, and a kind of open coffin for a head. A person was in the coffin, machinery threaded into their eyes and mouth. They groped blindly at the air as the machine spider-walked its way forward. When the giant smashed the machine, it bled from the resulting cracks, lurched back to a standing position, and then began firing lasers from turrets at the side. - Excerpt from Sundown 17.10
↑“Because he exists in multiple states at once, and the Machine Army, I’m told, does the same thing. They compress seeds of their material into dense matter and when they have something big and dense enough, even a boulder, they use them to house interdimensional pockets. The biggest machines and installments have those same pockets. If you nuke the area, that pocket leaks out, and before you know it, you’ve got an infestation again. He can get past that and do enough damage.” - Excerpt from Sundown 17.5
↑Get stationed in a place that's 'safe' from a PR perspective. Murderbeam isn't able to do much against the Machine Army, but might get stationed near Pueblo or the Pastor's area. - comment on Reddit by Wildbow
↑The second possibility is somewhat tricky, and becomes a balancing act. There are areas the PRT desperately wants to keep secure, and securing these areas becomes a punishment duty: [...] Eagleton, TN was evacuated, quarantined and is regularly patrolled after the Machine Army incident. [...] Naturally, the PRT doesn't want to put the wrong person on the wrong detail. Too violent a person in, say, Gallup or Gary would be a recipe for disaster, a spark to a powder keg. A mentally imbalanced or vulnerable person in Madison would be similarly disastrous. But find the right combination, like a trigger happy lunatic in Eagleton, and things are mostly fine, because they'll happily patrol and gun down the machines on the regular. Someone unambitious and lazy might let something slip through or grow out of control in Eagleton, but would be fine with the sleepy task of maintaining a watch on the periphery of Freedom. - comment on Reddit by Wildbow
↑You gotta figure that the PRT has thinkers that have analyzed whether it's worth doing that.
What you're liable to do with a nuke (because nukes don't really vaporize everything) is just spread out the machine 'seed' fragments and then you've got Machine Army everywhere. - comment by Wildbow on Reddit.
↑arandomperson1234:The Wardens have Valkyrie, Dragon (not a member, but probably available), and numerous thinkers. Wouldn't it be easy for them to just squish the machine army before it spreads out of control? Have them clear everything inch by inch, and have thinkers scour the land for anything they might have missed.
↑► Nutty Replied on August 17th, Y1 @ Boosher – This article, search for Nancy Y’s statement. People traveling across the US to get to portals are being warned about multiple threats. Word on the capevine is that with everyone having pulled out, all former quarantine zones are breached. In the US and elsewhere. Nilbog is the one everyone knows about. He’s in custody, his children aren’t. If you’re paying attention to hero groups and their movements, they’re making lots of trips out. They’re tired and people say they’re aloof. I say they’re fighting a hard fight and they’re keeping their distance from public and media because they don’t want us to know it. - Excerpt from Glow-worm P.1
↑“I don’t- this isn’t about me. Can you- can you let them know the Machine Army is this far north? They shouldn’t be on this side of the Raleigh chasm.” - Excerpt from Interlude 3 II
↑“A final titan, yet unnamed, as it just came to our attention. Auger, mercenary. He was on the front line against the Machine Army, and was caught out when the Red Queen’s line of assistance was interrupted. The Titan is apparently engaged with the Machine Army now. We’ll have more details soon. If anyone knows Auger, please reach out to us or talk to me over there.”- Excerpt from Radiation 18.2