The Serbians took heavy losses during this campaign, their army of 420,000 was decimated to around 100,000.
The Serbians lost a total of 1,1000,000 during the war - soldiers and civilians. This represented about 27% of Serbia's overall population, about 60% of their male population.
5. The Battle of Passchendaele
848,614 total casualties estimated
Also known as the Third Battle of Ypres, the aim of the battle was to breakthrough at the village of Passchendaele in West Flanders, Belgium and beat back the Germans.
Soldiers fought under miserable conditions, and both sides suffered
major casualties. The battle only allowed the British to acquire small territorial gains for their efforts.
Mud was a constant feature of the landscape, bogging down tanks and even drowning men. The allies lost a total of 448,614 men to the Germans 400,000.
4. The Battle of Verdun
976,000 total casualties
This battle was fought between the German and French armies between 21 February, 1916 to 18 December, 1916.
The French managed to recapture most of the ground they lost to the Germans, including Fort Douaumont, but lost some 542,000 casualties, while the Germans lost some 435,000.
Nearly 40 million artillery shells were exchanged during the battle, marking the area with craters which are still visible to this day.
Verdun was to the French and Germans what the Somme was to the British; a symbol of the horrors of war, and of the futility of World War I.
3. Battle of the Somme
1,219,201 total casualties