More than 500 000 soldiers died...in West Flanders alone:

Ypres: The City That Never Forgets

That's more than half the entire population of Ottawa. Can you picture it? Probably not, but we can try anyway.

"If people aren't reminded then it will all be forgotten and everybody will do the same stupid things that happened in the past."

-Brian Tarry

You could argue any lessons learned were forgotten within about twenty years.  All the more reason to take some time to think about it.