But you can still have leaders lead the frontline in spirit.
Basically, if leaders are going to send troops on an _offensive_ war/battle (not defensive war) there must be a referendum on the war.
If there are not enough votes for the war, those leaders get put on deathrow.
At a convenient time later, a referendum is held to redeem each leader. Leaders that do not get enough votes get executed. For example if too many people stay at home and don't bother voting - the leaders get executed.
If it turns out later that the war was justified, a fancy ceremony is held, and the executed leaders are awarded a purple heart or equivalent, and you have people say nice things about them, cry and that sort of thing.
If it turns out later that the leaders tricked the voters, a referendum can be held (need to get enough signatories to start such a referendum, just to prevent nutters from wasting everyone elses time).
This proposal has many advantages:
1) Even leaders who don't really care about those "young soldiers on the battlefield" will not consider starting a war lightly.
2) The soldiers will know that the leaders want a war enough to risk their own lives for it.
3) The soldiers will know that X% of the population want the war.
4) Those being attacked will know that X% of the attackers believe in the war - so they want a war, they get a war - for sufficiently high X, collateral damage becomes insignificant. They might even be justified in using WMD and other otherwise dubious tactics. If > 90% of the country attacking you want to kill you and your families, what is so wrong about you using WMD as long as it does not affect neighbouring countries?