RANKING

Largest battles by forces engaged

Great Retreat (1915) tops this list with 5,387,048 combatants engaged.

This ranks the 2,729 battles with documented force-strength estimates, of 3,680 battles catalogued — showing the top 100.

Every figure is a source-cited range, not a point estimate: rows are ranked on the midpoint but shown as their full low-to-high spread with the confidence grade behind them. Entries with no documented estimate are absent — nothing is imputed to fill a rank. The whole board is reproducible from the open dataset.

Largest battles by forces engaged
#	Battle	Forces engaged	Confidence	Sources
1	Great Retreat1915 · World War I	5,387,048	Medium	—
2	Battles of Rzhev1942 · Eastern Front	5,339,300	Medium	—
3	Case Blue1942 · Eastern Front	3,285,287 – 3,520,000midpoint ≈ 3,402,644	Medium	—
4	Vyazemsky operation1941 · Eastern Front	3,179,406	Medium	—
5	Battle of Berlin1945 · Eastern Front	3,066,750	Medium	—
6	1939 Invasion of Poland1939 · World War II	3,000,000	Medium	—
7	Vistula–Oder Offensive1945 · Eastern Front	2,653,600 – 3,003,600midpoint ≈ 2,828,600	Medium	—
8	Battle of the Oder–Neisse1945 · Eastern Front	2,800,000	Medium	—
9	Battle of Kursk1943 · Eastern Front	2,691,261	Medium	—
10	Battle of the Dnieper1943 · Eastern Front	2,634,943	Medium	—
11	Jassy–Kishinev Offensive1944 · Eastern Front	2,477,547	Medium	—
12	Meuse-Argonne1918 · World War I	2,450,000	Medium	loc_primary_timeline
13	Prague offensive1945 · World War II	2,370,700 – 2,420,700midpoint ≈ 2,395,700	Medium	—
14	1939–1940 Winter Offensive1940 · Second Sino-Japanese War	2,330,353	Medium	—
15	Battle of Voronezh1942 · World War II	2,285,800	Medium	—
16	East Prussian Offensive1945 · World War II	2,249,100	Medium	—
17	Soviet invasion of Manchuria1945 · Soviet–Japanese War	2,243,225	Medium	—
18	Operation Bagration1944 · Eastern Front	2,156,793	Medium	—
19	Battle of Smolensk1943 · World War II	2,102,600	Medium	—
20	Battle of Romania1944 · Eastern Front	2,000,000	Medium	—
21	Battle of Galicia1914 · World War I	1,950,000	Medium	—
22	Operation Desert Storm1991 · Gulf War	1,950,000	Medium	—
23	Battle of the Piave River1918 · World War I	1,911,000	Medium	—
24	2003 invasion of Iraq2003 · Iraq War	1,900,799	Medium	—
25	Baltic Offensive1944 · Eastern Front	1,889,142	Medium	—
26	Yangtze River Crossing Campaign1949 · Chinese Civil War	1,700,000	Medium	—
27	Siege of Leningrad1941 · Eastern Front	1,655,000	Medium	—
28	Donbass Strategic Offensive (August 1943)1943 · Eastern Front	1,453,000	Medium	—
29	Vienna offensive1945 · Eastern Front	1,441,800	Medium	—
30	Baltic Operation1941 · Eastern Front	1,441,000	Medium	—
31	Battle of Białystok–Minsk1941 · World War II	1,421,165	Medium	—
32	Tet Offensive1968 · Vietnam War	1,380,000	Medium	loc_primary_timeline
33	1975 spring offensive1975 · Vietnam War	1,380,000	Medium	—
34	Belgorod–Kharkov offensive operation1943 · World War II	1,344,000	Medium	—
35	Leningrad–Novgorod Offensive1944 · Eastern Front	1,322,000	Medium	—
36	Voronezh–Kastornoye Offensive1943 · Eastern Front	1,314,900	Medium	—
37	French invasion of Russia1812 · Napoleonic Wars	1,171,000 – 1,398,000midpoint ≈ 1,284,500	Medium	—
38	Battle of Dunkirk1940 · World War II	1,200,000	Medium	—
39	Hundred Days1815 · Napoleonic Wars	1,080,000 – 1,280,000midpoint ≈ 1,180,000	Medium	—
40	Hundred-Hour Ground War1991 · Gulf War	1,150,000	Medium	loc_primary_timeline
41	Operation Ichi-Go1944 · Second Sino-Japanese War	1,148,000	Medium	—
42	Battle of Greece1941 · World War II	1,130,000	Medium	—
43	First Jassy–Kishinev Offensive1944 · Eastern Front	1,130,000	Medium	—
44	Second Battle of Kharkov1942 · Eastern Front	1,115,300	Medium	—
45	Battle of the Seelow Heights1945 · Eastern Front	1,112,143	Medium	—
46	Operation Kutuzov1943 · Eastern Front	1,100,700	Medium	—
47	Easter Offensive1972 · Vietnam War	1,058,000	Medium	—
48	Invasion of Yugoslavia1941 · World War II	1,037,096	Medium	—
49	German invasion of the Netherlands1940 · World War II	1,030,000	Medium	—
50	Lvov–Sandomierz Offensive1944 · Eastern Front	1,004,144	Medium	—
51	Battle of Shanghai1937 · Second Sino-Japanese War	1,000,000	Medium	—
52	Battle of Xuzhou1938 · Second Sino-Japanese War	1,000,000	Medium	—
53	East Pomeranian Offensive1945 · Eastern Front	996,100	Medium	—
54	World War II in the Balkans1940 · World War II	995,000	Medium	—
55	Turkish involvement in the Syrian civil war2011 · Syrian Civil War	960,362 – 1,028,862midpoint ≈ 994,612	Medium	—
56	German invasion of Belgium (1914)1914 · World War I	970,000	Medium	—
57	Northern Expedition1928 · Chinese Civil War	800,000 – 1,100,000midpoint ≈ 950,000	Medium	—
58	Battle of Debrecen1944 · Eastern Front	939,152	Medium	—
59	Lake Naroch Offensive1916 · World War I	454,907 – 1,359,100midpoint ≈ 907,004	Medium	—
60	Battle of Bolimów1915 · World War I	889,446	Medium	—
61	Third Battle of Nanking1864 · Taiping Rebellion	870,000	Medium	—
62	Battle of Kolubara1914 · World War I	850,000	Medium	—
63	First Battle of the Masurian Lakes1914 · World War I	798,328	Medium	—
64	Battle of the Vistula River1914 · World War I	791,000	Medium	—
65	Battle of Kiev1943 · Eastern Front	731,943	Medium	—
66	Belgrade offensive1944 · Eastern Front	730,000	Medium	—
67	Operation Spring Awakening1945 · World War II	725,000	Medium	—
68	Soviet invasion of Poland1939 · World War II	620,000 – 820,000midpoint ≈ 720,000	Medium	—
69	Budapest offensive1944 · Eastern Front	719,000	Medium	—
70	Second Battle of the Masurian Lakes1915 · World War I	711,364	Medium	—
71	Crimean Offensive1944 · Eastern Front	692,400 – 718,370midpoint ≈ 705,385	Medium	—
72	Battle of Uman1941 · World War II	700,000	Medium	—
73	Operation München1941 · Eastern Front	690,385	Medium	—
74	Battle of the Scheldt1944 · World War II	680,000	Medium	—
75	Battle of Yehuling1211 · Mongol conquest of the Jin dynasty	665,000	Medium	—
76	Catalonia Offensive1938 · Spanish Civil War	650,000	Medium	—
77	Revolt of Czechoslovak Legion1920 · Russian Civil War	642,000	Medium	—
78	Donbass Strategic Offensive1943 · Eastern Front	640,909	Medium	—
79	Operation Dawn 61984 · Iran–Iraq War	640,000	Medium	—
80	Battle of the Bulge1944 · World War II	635,083	Medium	abmc_world_wars
81	Battle of Wuhan1938 · Second Sino-Japanese War	606,000 – 659,200midpoint ≈ 632,600	Medium	—
82	Battle of Caporetto1917 · World War I	610,400	Medium	—
83	Mongol conquest of the Song dynasty1235 · Mongol invasion of China	600,000	Medium	—
84	Battle of Nanjing1853 · Taiping Rebellion	590,000 – 610,000midpoint ≈ 600,000	Medium	—
85	Battle of Mukden1905 · Russo-Japanese War	562,250	Medium	—
86	Israeli invasion of the Gaza Strip2020 · Gaza War	549,500 – 569,500midpoint ≈ 559,500	Medium	—
87	Battle of Limanowa1914 · World War I	554,736	Medium	—
88	Battle of Okinawa1945 · World War II	542,815	Medium	—
89	Battle of Jiangnan (1860)1860 · Taiping Rebellion	540,000	Medium	—
90	Vyborg–Petrozavodsk Offensive1944 · Continuation War	526,500	Medium	—
91	Battle of Alegría de Álava1834 · First Carlist War	500,120	Medium	—
92	Battle of the Ch'ongch'on River1950 · Korean War	484,571	Medium	—
93	Battle of the Dukla Pass1944 · Eastern Front	478,000	Medium	—
94	Siege of Basra1987 · Iran–Iraq War	450,000 – 500,000midpoint ≈ 475,000	Medium	—
95	Hundred Regiments Offensive1940 · Second Sino-Japanese War	470,000	Medium	—
96	Colmar Pocket1945 · World War II	470,000	Medium	—
97	Battle of Stalingrad1942 · Eastern Front	457,000	Medium	—
98	Battle of Alesia-51 · Gallic War	378,000 – 520,000midpoint ≈ 449,000	Medium	—
99	Siege of Paris1870 · Franco-Prussian War	440,000	Medium	—
100	Serbian campaign1915 · World War I	440,000	Medium	—

Methodology

How it’s ranked. the midpoint of each battle's total forces engaged — the low and high strength estimates summed across every side, then averaged. Ties break by year, then slug.

What’s counted. every battle that carries at least one force-strength estimate in the catalogue. Each row's range is the sum of the per-side low and high figures we hold; the confidence column reflects the grades on those underlying estimates.

What’s excluded. battles with no force-strength estimate in the catalogue — absent, never imputed. Figures count forces engaged as sources recorded them, which for some entries is a theatre or campaign strength rather than a single field.

Coverage. This ranks the 2,729 battles with documented force-strength estimates, of 3,680 battles catalogued — showing the top 100. Coverage grows as the catalogue is enriched, so ranks can shift between harvests.

The board is computed directly from the catalogue and is reproducible from the public open dataset — see the methodology page for how the underlying figures are sourced and graded. Found an error? Corrections make the data better for everyone.