According to Russell T Davies in the documentary: The Making of The War Between the Land and the Sea, the Doctor Who spin-off was intended for significantly earlier production and release dates.

“It’s worth saying how long ago this production begins. I must have written The Star Beast and The War Between as the launch, as this is what we’re going to make. And this is our ambition. We then had to learn all this time how to make a programme with this budget and how to settle into Bad Wolf Studios. So we kept on intending to make The War Between — and never quite getting it. After Season One and then finally after Season Two, we did it.”

When the BBC first approach Davies about coming back to Doctor Who in 2021, The War Between the Land and the Sea was the first part of his pitch alongside the 60th Anniversary specials. “I had this idea separately first,” Davies told Radio Times.

Davies first publicly teased an “eight-word title” in Doctor Who Magazine 585 in December 2022, promising “big news soon.”

Davies clarified Doctor Who Magazine 598 in December 2023 that the previously-mentioned title had “been a bit delayed”, promising that “the reveal of those eight words” would come “any month now”.

Davies asked writer Pete McTighe to executive produce and write some of the episodes.

“I’ve been working on the show since 2023,” McTighe told Doctor Who Magazine. “After I handed in my first draft of Lucky Day, my episode for Season 2 of Doctor Who, Russell called me in for a meeting and said ‘Read this!’ and he gave me Episode 1 [of The War Between the Land and the Sea] that he’d already written, and he said ‘I’d love you to come on board and write some more episodes with me.'”

McTighe, tasked with writing Episodes 2-3 of the five-part spin-off, did some of his writing on the UNIT set in the studio during breaks filming Lucky Day in November 2023.

On 26 July 2024, The War Between the Land and the Sea and its principal cast was officially announced at San Diego Comic Con.

On 19 August 2024, production began with the cast and creatives participating in a read-through for all five episodes of the series.

The series transmitted in December 2025 in the UK and is expected to be available for streaming on Disney+ in 2026 “soon,” according to Pete McTighe at the Gallifrey One convention in Los Angeles I attended and have exclusively chronicled 8 February 2026.

“I hear that it’s happening soon. I don’t know — I don’t have inside info but all I’ve been told is that it’s happening soon. So I would imagine… But, you know — guys, just VPN it! Or buy the Blu-ray. The Blu-ray’s got lots of cool extra stuff in it. The Blu-ray has got deleted scenes in it. It’s got the documentary — the making of, which is really, really great. I’m hoping there’s a longer cut of that coming out sometime because there was so much footage. We were shooting footage the whole time. It was great.”

The The Making of The War Between the Land and the Sea documentary, no longer exclusive to the Blu-ray, is now available on YouTube.

On the same 8 February panel at Gallifrey One, McTighe revealed that there are 20 minutes of deleted scenes on The War Between the Land and the Sea DVD, Blu-ray and Steelbook, available for pre-order for a 23 February 2026 release in the UK.