It is the IWM relying on their research, not I, that said one of the most popular sayings of 1914 was "It will be over by Christmas". Follow the link I posted. I have never argued that it was a promise made by anyone. Just a popular expectation. Take it up with them.

What has winning to do with anything in this context?

It is not me that has suggested that winning the war justified all the deaths. I suggest you look up who said it and in what context as you will not believe it unless you do.