What is Severance in The War Between the Land and the Sea? Homo Aqua genocide explained

The War Between the Land and the Sea wrapped up on December 21, 2025. Instead of the all-out battle the title teased, Russell T Davies went for the bleak.

The BBC series introduced a twist called Severance, a human-made virus that wiped out 90% of the Homo Aqua population. It marks one of the darkest moments in the Whoniverse’s history.

At first, the series was going towards a sci-fi riff on our climate crisis. Ancient aquatic beings rise from polluted oceans and try to make a deal with humans. However, humanity creates bioweapons and calls it a day. That Severance plotline flipped the script. Now, this is not about environmental responsibility anymore. It’s more about how humans will always find a way to make things worse when they face an existential threat.

Kate Lethbridge-Stewart started off believing humans could do better, but by the end, she is shattered. The storyline of The War Between the Land and the Sea sets her as a future antagonist or at least a thorn in the Doctor’s side next time.

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The Severance genocide in The War Between the Land and the Sea

In The War Between the Land and the Sea, Severance was a secret biological warfare program executed by top-level personnel, among whom were General Gunsberg, General Dussolier, and Prime Minister Shaw. The series indirectly mentioned the program’s existence through obscure messages and hidden allusions, yet the complete atrocity of it was disclosed only in the finale’s tragic climax.

This virus hit the Homo Aqua species on their scales. It was supposed to fall off naturally, but it didn’t. Instead, they piled up, layer after layer, until they jammed up the poor creatures’ gills. They ended up drowning in the water that was supposed to sustain them.

The virus sabotaged their system, making those scales grow out of control until the Aquas suffocated. Nature can be cruel, but this was calculated.

The way they unleashed it was twisted, too. They slipped the virus into Barclay, Russell Tovey’s character, the human ambassador. He had no clue his own government had turned him into a biological bomb. Every time he met Salt at the Channel, thinking he was doing his diplomatic duties, he was actually passing along this nightmare. Those meetings were not peace talks. They were more like premeditated murder, wrapped up in military orders.

The next morning, everyone woke up to complete chaos. People woke up to beaches filled with Homo Aqua bodies, from Brown’s Bay all the way to Antigone Bay. It was everywhere. The death toll was off the charts. Scientists figured out the virus had speed-run across the globe through some algae network that linked all the Homo Aqua together. Turns out that deep connection that made them strong just made them easy targets for a hit like this.

The worst part is that only about 10% made it. One in ten, that’s it. Whoever created this virus wanted a few to survive. Maybe to dodge accusations of full-blown genocide, or maybe just to show off how precise their bioweaponry game is. Either way, it’s chilling.

Also Read: Will The War Between the Land and the Sea Season 2 happen? Possibilities explored

The political conspiracy in The War Between the Land and the Sea

UNIT, the United Nations Intelligence Taskforce, led by Kate Lethbridge-Stewartthey kept making noise about ‘diplomatic solutions.’ Meanwhile, a bunch of suits and brass in the government and military were scheming up something way nastier. That’s how “Severance” was born, or at least whispered about in backrooms and encrypted chats.

Kate started digging, and she found little breadcrumbs tying everything to PM Shaw and the late Sir Keith Spears. Shaw shrugged and said that the word could mean anything. Meanwhile, Generals Gunsberg and Dussolier were busy shuffling Barclay down to the beach for negotiations, when really, he was their delivery guy, except he didn’t even know it.

And let’s not forget Las Clementi. It was supposed to be a think tank, but it’s more like a paranoia factory. Their big idea was to wipe out Homo Aqua. And none of these people care about things like “democracy” or “oversight”. They are convinced they are the last line of defense for humanity, even if it means crossing into genocide territory.

In The War Between the Land and the Sea, Kate corners Shaw and lays it out flat. She says his days are numbered, that the economy is about to belly flop, he will be out in half a year, and some new hardliners will roll in with the wave of anti-Aqua hysteria. War will just keep spinning around with same old cycle.

But Kate reminds him that she will still be there, waiting. Promising a day of reckoning.

The hollow victory in The War Between the Land and the Sea

When Salt finally came back to face humans after the genocide, she didn’t grovel, but her surrender speech was painful to watch. The Homo Aqua basically said the humans won, but made it sound like the whole war had just been an inconvenience. Now they were terrified, or at least said they were, ready to do whatever humans wanted, just to avoid getting wiped out completely.

The so-called peace deal was a total humiliation. Humans smugly announced they would “let” the Homo Aqua survive, but only if they stayed way down in some trench in the Pacific, boxed in and safe from pollution, supposedly. But everyone knew what it was: not a sanctuary, not really, more like a fenced-in reservation. Or worse, a trap. A hunting ground in disguise.

And then Salt dropped one last twist. The Homo Aqua had hidden all their advanced tech in places so deep in the ocean that humans didn’t stand a chance of finding it. So humans “won” the war, but they got nothing out of it. The original Earthlings kept their mysteries locked away beneath miles of water, out of reach.

Before she left, Salt aimed some serious shade at the people behind the genocide. She said, “water will find you,” and then we see the visions (or were they threats?) of Prime Minister Shaw and Generals Dussolier and Gunsberg drowning. Is this a prophecy, a warning, or just a mind game? She left it open.

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Also Read: The War Between the Land and the Sea ending explained: Barclay and Salt tragic yet hopeful end