number of soldiers mobilized by belligerents in WW1?

Answer 1

Here are the numbers in 1914 and during the war.

Countries in First World War

Standing Armies
& Reserves in
August 1914

Mobilised
Forces in
1914-18

Russia 5,971,000; 12,000,000
France 4,017,000; 8,410,000
Great Britain 975,000; 8,905,000
Italy 1,251,000; 5,615,000
United States 200,000; 4,355,000
Japan 800,000; 800,000
Romania 290,000; 750,000
Serbia 200,000; 707,000
Belgium 117,000; 267,000
Greece 230,000, 230,000
Portugal 40,000; 100,000
Montenegro 50,000; 50,000
Germany 4,500,000; 11,000,000
Austria-Hungary 3,000,000; 7,800,000
Turkey 210,000; 2,850,000
Bulgaria 280,000; 1,200,000