Nobody in their right mind is keen for a war. Nobody would fight in one unless they believed they really had no other choice. I don't blame the people who would runaway to relative safety if the option is available.

But. It's clearly a massive security issue.

> If you’re that keen, go join the reserves?

There is not currently a war, and if there was, there wouldn't be a choice but to join.

Anyone who thinks war might be fun should watch some of the interviews with veterans from the “great” wars on YouTube.

That's a valid statement that nobody in this comment chain was disputing. It is exactly why the person you're responding to is assuming anyone who can leave, will leave, in that event (and why "you should join the reserves if you're that keen" is an irrelevant comeback-- nobody was saying anyone's keen, only that people aren't keen and will leave to avoid it if able).