You act as if this is a modern social phenomenon. The general public never favours war. It's one of the hardest, riskiest things for a politician to push for. It almost always ends their career. Hell even before WW1 if you had polled the UK you would have found most people would probably want us to ignore our obligations to Belgium and France.
Except that things have changed. Maggie taken us to war over the Falklands saved her government.
Looking at polls they were heading for a massive defeat but suddenly beating the Argies gave her a good majority again.
The risk there of course is if you lose....................