The seriousness of blood shed can be gauged by

As small as a physical wound causing blood loss. The wound leaves an eternal mark on the body of the child or grown up even after it heals, which cannot be undone. The person is reminded of, by looking at it for life.

And --

As big as a war, which leaves an unerasable mark on the battlegrounds marred by fallen warriors that people remember timelessly.

When, the story of just this one person is remarkable, sometime reiterated for life.

Then, million lives lost during a war undoubtedly have a message resonating loud and clear for the world that carries forward for a millennia and yugas.