Around 9–11 million soldiers were killed in World War I, with many historians and reference works using a midpoint estimate of about 10 million military dead worldwide.

Key figures

  • Most modern estimates put military deaths at roughly 8.5–10 million, counting those killed in action and those who died later from wounds or disease.
  • Civilian deaths are usually estimated at 6–13 million, caused by famine, disease, displacement, and direct violence.
  • In total, World War I likely caused well over 15 million deaths when soldiers and civilians are combined, with some estimates going significantly higher.

Why the numbers vary

  • Record-keeping was incomplete or lost in several countries, especially those that experienced revolution or collapse, so historians often work with ranges instead of a single precise total.
  • Different studies count deaths differently: some include only battlefield deaths, while others add deaths from disease, imprisonment, and long-term effects of wounds.

By side (very broad)

  • The Allied (Entente) powers together lost roughly 6 million military personnel, while the Central Powers lost around 4 million, leading to the common 10‑million estimate for soldiers.
  • Individual national totals (like for Russia, France, Germany, Austria‑Hungary, the UK, Italy, and others) each run into the hundreds of thousands or over a million, contributing to the global total.

Historical context

  • These losses came from trench warfare, artillery barrages, machine guns, and disease in crowded front-line and rear-area camps.
  • The scale of soldier deaths in WW1 shocked contemporaries and directly influenced politics, society, and attitudes toward war in the decades that followed.