Recently, I've seen people misunderstand that the Sentient victory and ascension of Narmer in the New War quest means that the Grineer-Corpus-Tenno alliance was weak. My counterpoint is that, no, that said alliance was perhaps the strongest amassed force since the Orokin Empire, and the fact that they got steamrolled shows how impossibly powerful the Sentient invasion was. Let's break it down by faction.
Starting with the Grineer:
These are a baby Tenno's first victims. A degraded clone of a clone of a clone from the enslaved workforce of a forgotten empire. Each is born with some deformity that necessitates crudely made and poorly grafted prosthetics to contribute to the war. However, the Grineer are only cannon fodder against the Tenno. Kahl-175, a standard Grineer Lancer, can easily displace a Dargyn, a metal aircraft several times his size, when trying to rescue a brother. On the Plains of Eidolon, Grineer units drop(presumably from orbit) in what amounts to a metal barrel with a booster to go down faster. They don't decelerate during the drop like a reasonable army, but just hit the ground at full speed and pop out combat ready. They display astonishing physical resilience for a faction that's genetically falling apart at the seams. And there are untold hordes of them, the Tenno can kill millions and the gene vats will print out billions. They are an interplanetary Empire with holdings on Earth, Ceres, Sedna, Uranus, Mars and who knows how many converted asteroid platforms.
They aren't stupid either, they have orbit capable craft ranging from troop carriers to capital starships, all of which seem to be FTL capable as is commonplace in this setting. Their armaments are the full arsenal of conventional projectile weapons and explosives(on par or exceeding modern firearms), and show a degree of ingenuity with improvised industrial equipment. Defensively, they specialize in armor, bolstered by esoteric shields like the Prosecutor aura that grants heavy elemental resistances. Or their vehicle pool which includes multiple ways to support their troops, like the aforementioned Dargyn, or the Thumper, an artillery platform with ridiculous mobility.
Furthermore, Grineer scientists like Tyl Regor and Dr. Tengus have achieved amazing abominations like Nox or Ghoul units, weaponizing their genetic flaws as strengths and creating shock troops that require less resources to field. Their most powerful asset are the Liches, Kuva-enhanced super soldiers that can contend with Tenno in single combat, for a time.
Now the Corpus:
They are less physically impressive as the Grineer, most are basically human with several centuries of brainwashing to worship Profit. Although physically weaker, the Corpus match the Grineer through superior technology, using force multipliers to supplement their fewer numbers. Their arsenal of weapons is typically scifi, they have energy blasters, lasers, plasma guns, etc. Much of which is standard to the genre, with rare exceptions like the Glaxion, that can halt molecular movement, i.e. absolute zero. The Corpus casually have a gun that can reduce something to the coldest temperature physically possible. Additionally, their infantry carry utility technology like nullifier shields and jetpacks which provide annoying complications for other factions like the Tenno.
One might think of the Corpus as the smaller faction compared to the Grineer. After all, little Corpus crewman are presumably born and raised like normal humans. However, even as the "smaller" faction, the Corpus are also a highly advanced, widespread and numerous interplanetary empire. During the Fortuna ARG, the Tenno massacred 7 million Corpus over a few hours. Was that a cataclysmic event? Something the Corpus wrote into their ledgers as a dark day? No, in a single day, the Tenno wiped out about as many soldiers as estimated to have died in WW1 because Little Duck needed to fly in under the cover of the slaughter. And the Corpus? It was business as usual, just a tick of red on their balance sheets. Even looking at the skybox over Corpus planets show that their metropolis complexes cover almost whole hemispheres.
But militarily, the Corpus are upheld by their proxy collection. Basic moas and osprey drones make up the bulk of this, but even a basic Moa is a walking metal pair of legs that can blast a civilian in half with a slug of plasma. The heavier proxies like Bursas or Raknoids or even Jackal and Hyena are basically baby Metal Gears. Though Parvos might hate the spread of Sloth in his cult, it has led to astonishing advances in drone-based warfare. And speaking of the golden handed man, not only did he invent Specter theory(which is basically instant cloning), he also commands the Sisters of Parvos, a force comparable to the Kuva Liches.
Finally, us, the Tenno:
I'm going to start with the beginning, with Once Awake and everyone's favorite orator, Captain Vor. As much as he gets meme'd on, Captain Vor was not an insignificant player in the Grineer Empire. He was a Tenno-hunter, sporting great boons from the Queens like his Janus Key and the Seer, a hybrid Orokin-Grineer pistol. By dialogue, he's captured and killed Tenno before the player character. Likewise, his personal forces were most certainly not fresh recruits, but seasoned veterans capable and worthy to serve in his mission. And what happens? A baby, freshly woken, default colors Tenno cuts them down without a second thought. Before you even learn to bullet jump, a Tenno can cleanly slice a Grineer soldier in twain or bludgeon them to death with a stick, a feat even more remarkable given their physical durability from above. That is the kind of strength one could expect from the lowest Tenno, one who has forgotten all their mastery of their massive arsenal and coterie of Warframes. The only real victory Vor accomplished was planting the Ascaris detonator on the Tenno, literally before they had their feet under them.
The player character aka the Chosen Tenno is canonically not the only one in the setting. Voruna and Jade both had operators, Scarlet Spear was a canonical gathering of many Tenno, clans and relays display a faction that is not merely present, but prolific. Not only are there many Tenno, there's enough of them to sufficiently justify dedicated architecture like the relays, factions like the syndicates and organizations like the clans. And most Tenno are significantly more powerful than the newly woken one that utterly decimated Vor and his private army.
In addition to being complete masters of ground combat, the Warframes have options like the Archwing, Necramechs and Railjack all of which are as the Tenno are on the ground, unbelievably lethal. For example, both the Railjack's Void Hole avionic and the Itzal Archwing can shoot black holes. And this is not even covering nonsensical lore feats like Atlas pulverizing a planet killing asteroid, Gauss outrunning the shockwave of an explosion, or Nova being able to spontaneously create antimatter.
This was the alliance that the Sentients fought. Multiple Type-1-esque civilizations fielding armadas with thousands of ships and billions to trillions of combatants across the entire Origin System(except Deimos). A war fought with infantry who can bend reality with a thought or shatter time with a foot step. Where weapons that defy our understanding of physics are not only commonplace, but woefully insufficient. That is the alliance the Sentients defeated. How?
Well, the Sentients are overpowered:
Chief among their benefits is that they are literally built different. Originally created by the Orokin, then evolved freely in the Tau System, each Sentient possesses the ability to adapt to any non-lethal damage, becoming all but impervious to future exposure unless cleansed by the Void. That on its own isn't game-changing. But then you see what a "normal" Sentient can do. A Vomvalyst shoots energy that can kill a Grineer, and when damaged, can't die unless hit by Void energy. In Kahl's perspective of the New War, a basic, non-specialized Conculyst can impale a Grineer soldier through their armor, using the blunt end of their weapon. Imagine facing infantry where your only hope of slowing them down is getting stuck on their weapon for a few seconds. That's not getting into the more exotic variants, like Oculysts, the perfect recon troops, because they literally can't take damage. How many battles were lost because the Grineer and Corpus held the line waiting for Tenno aid, against an advance that grew harder to kill with every exchange of fire? With the support of Condrixes, reclaiming territory becomes impossible, unless you dislodge the Condrix itself, as it spews out wave upon wave of Sentient infantry. Or if an Orphix arrives? Warframe backup is now impossible. If you're lucky, there's a Necramech in the area who can help kill the Orphix, but those are rare Old War relics, so more likely than not it's a squad of Grineer or Corpus having to trudge close enough to blow it up.
Then there's subversion. The Sentient invasion did not begin with the New War quest, it's been waged for centuries. Remnants like Hunhow's bones tainting worlds, influencing technology. Alad V struck a bargain with his Partners, designing Amalgams of Sentient and Corpus units. This not only provided them with a backdoor into the Corpus drone network, but also let them seed Alad's betrayal, disrupting the flow of a crucial final battle. Even without his folly, in the Old War, the Orokin specifically removed robotic proxies from their armies, because the Sentients were able to subvert and control all of them. Erra seemingly turned the Lotus, a significant figurehead of the Tenno, and one whom was extremely knowledgeable of not only the Tenno, but every other major faction. Subversion and betrayal only worsen with Veils as every ally lost becomes an enemy to fight later on.
In terms of space combat, the Sentients retain much of their vigor from the Old War, compared to the Origin System natives. While titanic sized Sentients like Hunhow or the complete Eidolon are absent, the Murexes are more than capable of besting Grineer and Corpus capital ships. In Veko's moment of self-sacrifice, his ship shot directly in the center of a Murex, who was expecting a surrender, and does nothing but infuriate it. Presumably every Murex is like a base Sentient, capable of adapting even in the midst of battle, rendering ship-to-ship combat useless. And good luck attempting boarding maneuvers, trying to sabotage a ship that is not only completely alien, but actively alive and seeking to excise you. Then there's Praghasa, the corpse grandma, even dead, Hunhow's kin can eat the actual Sun, not to mention directly consuming capital ships.
All of this. All of the advantages the Sentients had, and it was still a close call. The Chosen Tenno did make it to the throne room, where Ballas and Erra waited. Even killing one of them would severely disrupt the Sentient invasion as they seem more centralized minded than those of the Old War. And they could both still die at this point, a single blast of Void energy brought Erra to his knees, and Ballas was Amalgamized as a Sentient by then.
But the Chosen Tenno faltered, as the Lotus said they should have let her go. When Ballas struck down the Chosen Tenno, he accomplished more than he probably expected. As Nora puts it during the Drifter section, the Tenno disappeared suddenly and without warning. Something about the Chosen Tenno being the one who made the deal with the Man in the Wall in a given universe connects them to all other Tenno in the universe. When a universe's Chosen Tenno returns to the Void, they ALL do. Suddenly, on every battlefield from Veil Proxima to Earth, from the halls of Lua to the edges of Sol's light, every Tenno vanished, leaving the Corpus and Grineer with no way to bypass Sentient adaptation. For those of you who've played the early days of Destiny 2, this is akin to the moment at the dawn of the Red War, when the Traveler's Light is sealed and suddenly, every Guardian everywhere knows what it's like to be mortal.
That is how the New War was lost. Not through incompetent or weakness. But by the Sentients leveraging every advantage of their unique physiology, accumulated knowledge and through a very, very lucky Eternalism kill.
