I've been watching the Hammer and Bolter animated series on Warhammer+, and I'm reviewing each episode as I watch it. There may be very minor spoilers, but ideally no more than you'd get from the episode description.
In this episode, the comms are down in the Astra Militarum trenches, so a Galipoli-style foot messenger runs from HQ to the frontline to get the commander's orders. He's just a runner, and there are aliens actively attacking, so it's pretty harrowing. He gets an armed escort back to HQ, but the journey is doubly terrifying because the aliens have broken through the lines. There's shooting, there's death, and eventually the messenger finds the strength to shoot at things.
"Cadia stands" is a war cry for the trenches, because although Cadia actually fell years ago, it stands within their hearts. By the end of the episode, the runner understands this, and intones it as he exits the HQ, having successfully delivered the commander's orders.
This episode is OK sci fi. I'm biased against it because I didn't love the plot of a coward turning into a proud soldier through witnessing atrocity. There were some really good sci fi elements, though. There's enough shooting of aliens to make it a fun 15 minutes, and some interesting concepts of sneaky explosive mines.
This episode is OK Warhammer 40,000. It's not very dynamic. They're in trenches, they try to hold the line. The aliens are deadly. I think I'd have enjoyed this more if it had been set on a spaceship.
All images in this post copyright Games Workshop.