is this a good idea or not?

ok, so I've decided to write a world war two book. about Canadian marines specifically.
aaaand, I wanna kill them all off, half way through the book. just, all dead.
because I want the rest of the book to be about them still out there, not able to go home, even once the war is over. (wow I already feel like a mean author.) and I had an idea to toss some fantasy in too, that they're still out there to protect the living from something.
but anyway, I was wondering if this sounds like a good idea, or at least if it sounds interesting.

I've already done a bit of research too, and I've picked a few battles that they might die in. so,,, yea :3

That sound cool! I would definitely read that.
And I love the changes of genre.

I love this idea! You can really do a lot if you handle it correctly. I think that their deaths should definitely be a plot twist, but it should also be heavily foreshadowed throughout the beginning of the book. Have them express fears of never being able to come home. Have them talk about home often, and make sure they all have someone/something they want to get back to. Make the reader root for them and hope they survive. I'd also recommend making the tone semi-lighthearted, so that the tonal shift when they all die will help the plot twist feel more surprising. I seriously think this idea has a lot of potential. Good luck :D

ahhh! thanks for the feedback! I love your ideas for the foreshadowing too. ^^
also, I wanted to be extra mean, aaand maybe have them die right before the war ends.
since the war ended in September 1945, I want them to maybe die in 1944, although I did find one battle in April 1945 they could die in, which would sting a lot more I feel.
I'm gonna be such a mean author, I'm excited!

But
What if, like
Maybe one would survive to tell the tale?
That would even more heart-breaking, have one person tell the families who lost their sons, fathers, husbands, ect. what happened to them and you can showcase the families' reactions and stuff
That makes it more heart-breaking

ISN'T THAT RIGHT, SARAH

YES (also i see what you did there)
What if the last guy is the only one who didn't really have a family? What if he pretended to have someone to return to, but instead he ends up homeless and forced to share horrible news with his comrade's families?
Just a (depressing) thought. :D

I'm sobbing I love you people this book is gonna heart-breaking I'm excited!!!!

Glad we could help