[dmichulke]

I think the British also guaranteed Poland, so they we're already in in September '39

[breischl]

But when the line was conceived and built, they couldn't have known Germany would invade Poland first.

[mrguyorama]

Wasn't that that "Quiet war" ie, both france and great britain had guaranteed poland, and declared war, but didn't actually push out troops or really do anything until france was invaded?

[goodcanadian]

Phoney War. War was declared, but no real fighting was going on:

https://en.wikipedia.org/wiki/Phoney_War