Deadliest single days of World War I

World War I was fought on many fronts around the world from the battlefields of Europe to the far-flung colonies in the Pacific and Africa. While it is most famous for the trench warfare stalemate that existed on Europe's Western Front, in other theatres of combat the fighting was mobile and often involved set-piece battles and cavalry charges. The Eastern Front often took thousands of casualties a day during the major offensive pushes, but it was the west that saw the most concentrated slaughter. It was in the west that the newly industrialized world powers could focus their end products of the military–industrial complex. The deadliest day of the war was during the opening days of the conflict. The Imperial German war council had initiated the Schlieffen Plan which involved multiple armies flooding through the borders of Belgium and France. On August 22, 1914, during the Battle of the Frontiers, five separate French armies engaged the German invaders independently of each other. Across all those battlefields, on that single day, 27,000 French soldiers lost their lives protecting their country.^[1]

Will Longstaff's Menin Gate at Midnight

Moscow City Brotherly Cemetery in 1915

Sandweiler German war cemetery in Luxembourg

The term casualty in warfare is often misunderstood. It often refers not to those who are killed on the battlefield but to those who can no longer fight. That can include disabled by injuries, disabled by psychological trauma, captured, deserted, or missing. A casualty is, by definition, a soldier who is no longer available for the immediate battle or campaign, the major consideration in combat. The number of casualties is simply the number of members of a unit who are not available for duty. For example, on March 21, 1918, during the opening day of the German spring offensive, the Germans casualties are broken down into 10,851 killed, 28,778 wounded, 300 POW (or taken prisoner) for a total of 39,929 casualties.^[2] The word casualty has been used in a military context since at least 1513.^[3] In this article, the numbers killed refer to those killed in action, killed by disease, or killed by their wounds.

Western Front

Main article: Western Front (World War I)

Country	Battle, siege, or offensive	Date	Number killed on this day	Total killed during WWI	% of total killed	References
France	Battle of the Frontiers	August 22, 1914	27,000	1,357,000[4]	2%	[5]
United Kingdom	Battle of the Somme	July 1, 1916	19,240	744,000[6]	3%	[7]
German Empire	Kaiserschlacht	March 21, 1918	10,851	2,037,000[8][9]	0.53%	[2]
Canada	Battle of Vimy Ridge	April 9, 1917	2,414	56,639[10]	4%	[11]
Australia	Battle of Broodseinde	October 4, 1917	1,282	61,527[10]	2%	[12]
New Zealand	First Battle of Passchendaele	October 12, 1917	847	18,166[13]	5%	[14]
Belgium	Massacre at Dinant	August 23, 1914	674	38,170[15]	2%	[citation needed]
First Portuguese Republic	Battle of the Lys	April 9, 1918	500~[A 1]	7,222[15]	7%	[16]
United States	Battle of the Argonne Forest	October 4, 1918	418	116,516[17]	0.36%	[18]
Newfoundland	Battle at Beaumont-Hamel (Somme)	July 1, 1916	310	1,204[10]	26%	[19]
South Africa	Battle of Delville Wood	July 18, 1916	253	7,121[10]	4%	[20]
Russian Empire (until 1917)				1,700,000[15]
Thailand SEF (from 1918)	Base Hospital No. 57	February 7, 1919	2[A 2]	19[21]	11%	[21]

Eastern Front

Main article: Eastern Front (World War I)

Country	Battle, Siege, or Offensive	Date	Number killed on this day	Total killed during WWI	% of total killed	References
Russian Empire				1,700,000[15]
German Empire				2,037,000[8][9]
Romania				335,706[22]
Bulgaria				101,229[A 3][23]
Austria-Hungary				1,200,000[24]
Ottoman Empire				325,000[A 4][24]

Naval battles

Main article: Naval warfare of World War I

Country	Battle, siege, or offensive	Date	Number killed on this day	Total killed during WWI	% of total killed	References
United Kingdom	Battle of Jutland	May 31, 1916	6,094	744,000[6]	1%	[25]
German Empire			2,551	2,037,000[8][9]	0.13%
Italy	SS Principe Umberto	June 8, 1916	1,926	460,000[15]	0.48%	[26]
France	SS Gallia	October 4, 1916	1,338	1,357,000[4]	0.1%	[27]
Austria-Hungary	SS Linz	March 18, 1918	697[A 5]	1,200,000[24]	0.06%	[28]
Russian Empire	Pallada	October 11, 1914	597	1,700,000[15]	0.04%	[29]
Empire of Japan	Kawachi	July 12, 1918	500–700[A 6]	4,661[30]	13%	[31]
United States	USS Cyclops	After March 4, 1918[A 7]	309	116,516[17]	0.3%	[32]
Ottoman Empire	Barbaros Hayreddin[A 8]	August 8, 1915	258	325,000[A 9][24]	0.07%	[33]
Canada	HMHS Llandovery Castle	June 27, 1918	234	56,639[10]	0.4%	[34]

Gallipoli campaign

Main article: Gallipoli campaign

Country	Battle, siege, or offensive	Date	Number killed on this day	Total killed during WWI	% of total killed	References
Ottoman Empire	Third attack on Anzac Cove	May 19, 1915	5,000~	325,000[A 10][24]	2%	[35]
France	First Battle of Krithia	April 28, 1915	1,001[A 11]	1,357,000[4]	0.7%	[36]
United Kingdom	Battle of Scimitar Hill	August 21, 1915	1,497[A 12]	744,000[6]	0.2%	[38]
Australia	ANZAC Cove	April 25, 1915, August 7, 1915[A 13]	755	61,527[10]	1.2%	[39][40]
New Zealand	Battle of Sari Bair	August 8, 1915	507	18,166[13]	3%	[41][42]
India	Third Battle of Krithia	June 4, 1915	207[A 14]	42,448[A 15][A 16][45]	0.5%	[46]

Italian Front

Main article: Italian Front (World War I)

Country	Battle, Siege, or Offensive	Date	Number killed on this day	Total killed during WWI	% of total killed	References
Italy				460,000[15]
France				1,357,000[4]
United Kingdom				744,000[6]
German Empire				2,037,000[8][9]
Austria-Hungary				1,200,000[24]

Macedonian front

Main article: Macedonian front

Country	Battle, Siege, or Offensive	Date	Number killed on this day	Total killed during WWI	% of total killed	References
Greece				6,000~[15]
Serbia				127,535[A 17][15]
Italy				460,000[15]
France				1,357,000[4]
United Kingdom				744,000[6]
Russian Empire				1,700,000[15]
German Empire				2,037,000[8][9]
Bulgaria				101,229[A 18][23]
Austria-Hungary				1,200,000[24]
Ottoman Empire				325,000[A 19][24]

See also

• Surviving American units with the highest percentage of casualties per conflict
• List of maritime disasters in World War I
• World War I casualties
• List of battles with most United States military fatalities
• General Pershing WWI casualty list

Notes

1. Portuguese faced the Germans for three days, from April 9–11, 1918. Around 500–700 were killed in action, mostly on the first day
2. Two died after the war had ended. Three others died during the war on three different days:
   February 11, 1918
   March 1, 1918
   October 21, 1918
3. Killed 48,917 + Died of wounds 13,198 + Accidental deaths 888 + Died of disease 24,497 + Missing presumed dead 13,729
4. Killed 50,000 + Died of wounds 35,000 + Died of disease 240,000
5. Hundreds of unregistered passengers, mostly Austro-Hungarian soldiers returning from leave who boarded Linz illegally at Zelenika. Some estimations go as high as 2,700 people killed
6. Sources differ widely on the exact number of men killed. Gardiner and Gray and Jentschura, Jung and Mickel agree on 700, but Lengerer says 600 and Kingsepp gives 618 killed from a crew of 960
7. Cyclops was last seen outside of Baltimore on March 4, 1918
8. On 3 May 1915 the steamer Gul Djemal with 4000 troops on board was torpedoed and sunk by HM Submarine E-14. The number of casualties are unknown; the British claimed many were lost, while German and Turkish records report limited casualties only.
9. Killed 50,000 + Died of wounds 35,000 + Died of disease 240,000
10. Killed 50,000 + Died of wounds 35,000 + Died of disease 240,000
11. 14,000 Allied troops participated in the battle and suffered 2,000 British and 1,001 French casualties ^[36]
12. 5,300 casualties out of the 14,300 soldiers who participated ^[37]
13. Both days saw 755 Australians die
14. 220 Indians died on all fronts^[43]
15. In Gallipoli 1,358 Indians died, 3421 were wounded for a total of 4,779 casualties^[44]
16. Excludes followers^[45]
17. Killed 45,000 + Missing presumed dead 82,535
18. Killed 48,917 + Died of wounds 13,198 + Accidental deaths 888 + Died of disease 24,497 + Missing presumed dead 13,729
19. Killed 50,000 + Died of wounds 35,000 + Died of disease 240,000