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In terms of sheer numbers, the cost of World War I in human life was staggering beyond any war that had preceded it. The number of civilian casualties is unknown but is certainly in the millions. The chart below shows those nations that lost 100,000 men or more (killed, wounded or missing) in combat. Some smaller nations had fewer casualties but a much smaller population; hence, they deployed a smaller military force but suffered a high percentage of casualties. Montenegro, for example, suffered “only” 20,000 casualties—but from a force of 50,000 that reflected a loss of 40%.

Beyond its own battlefield casualties, the War to End War spawned the Russian Civil War, the Balkan Wars and, many would argue, the Second World War. With the end of World War I, the Ottoman Empire was dismantled and national boundaries drawn by Britain and France without regard to ethnicity, religious affiliation, or traditional homelands. The deaths in the Mideast (and worldwide in jihad-inspired terrorist attacks) as a result of those decisions continue to the present day.

Nations listed are color-coded to reflect the year they entered the war and the side on which they fought, the Allied Powers (or Entente) or the Central Powers. Numbers are rounded; sources disagree about actual numbers.


Nation Casualties
Casualties as
% of troops
Date Entered War Which
Russia  9,150,000  76%  Nov 2, 1914;
exited war
Mar 3, 1918
Allied Powers
 Germany  7,143,000  65%  Aug 1, 1914  Central Powers
 7,000,000  90%  Jul 28, 1914  Central Powers
 France  6,161,000  73%  Aug 2, 1914  Allied Powers
 Britain &
 3,190,000  36%  Aug 4, 1914  Allied Powers
 Italy  2,197,000  39%  May 23, 1915  Allied Powers
 Turkey (Ottoman
 975,000  34%  Aug 30, 1914  Central Powers
 Romania  536,000  71%  Aug 27, 1916; exited
May 7,  1918; rejoin-
ed war Nov 10, 1918
 Allied Powers
 Serbia  331,000  47%  Aug 6, 1914  Allied Powers
 USA  323,000    7%  Apr 6, 1917  Allied Powers
 Bulgaria  267,000  22%  Oct 14, 1915  Central Powers