1914

  July 28

Austria on Serbia

  Aug. 1

Germany on Russia

  Aug. 3

Germany on France

  Aug. 4

Germany on Belgium

Great Britain on Germany

  Aug. 5

Montenegro on Austria

  Aug. 6

Austria on Russia

Serbia on Germany

  Aug. 8

Montenegro on Germany

  Aug. 12

France on Austria

Great Britain on Austria

  Aug. 23

Japan on Germany

  Aug. 25

Japan on Austria

  Aug. 28

Austria on Belgium

  Nov. 4

Russia on Turkey

Serbia on Turkey

  Nov. 5

Great Britain on Turkey

France on Turkey

1915

  May 23

Italy on Austria

  June 3

San Marino on Austria

  Aug. 21

Italy on Turkey

  Oct. 14

Bulgaria on Serbia

  Oct. 15

Great Britain on Bulgaria

Montenegro on Bulgaria

  Oct. 16

France on Bulgaria

  Oct. 19

Russia on Bulgaria

Italy on Bulgaria

1916

  March 9

Germany on Portugal

  March 15

Austria on Portugal

  Aug. 27

Romania on Austria

  Aug. 28

Italy on Germany

Germany on Romania

  Aug. 30

Turkey on Romania

  Sept. 1

Bulgaria on Romania

1917

  April 6

U.S. on Germany

  April 7

Panama on Germany

Cuba on Germany

  April 13

Bolivia severs relations with Germany

  April 23

Turkey severs relations with U.S.

  June 27

Greece on Austria, Bulgaria, Germany, and Turkey

  July 22

Siam on Germany and Austria

  Aug. 4

Liberia on Germany

  Aug. 14

China on Germany and Austria

  Oct. 6

Peru severs relations with Germany

  Oct. 7

Uruguay severs relations with Germany

  Oct. 26

Brazil on Germany

  Dec. 7

U.S. on Austria

  Dec. 8

Ecuador severs relations with Germany

  Dec. 10

Panama on Austria

  Dec. 16

Cuba on Austria

1918

  April 23

Guatemala on Germany

  May 8

Nicaragua on Germany and Austria

  May 23

Costa Rica on Germany

  July 12

Haiti on Germany

  July 19

Honduras on Germany