| Dates |
Events |
|
| September 25 – October 15
|
Battle of the Hohenzollern Redoubt, a phase of the Battle of Loos.
|
|
| September 25 – November 6
|
Second Battle of Champagne.
|
|
| October 7 – December 4
|
Serbia is invaded by Germany, Austria-Hungary, and Bulgaria.
|
Details
|
| October 14
|
Bulgaria declares war on Serbia
|
Details
|
| October 14 – November 9
|
Morava Offensive, a phase of the Central Powers Invasion of Serbia, Bulgarians break through Serbian lines.
|
|
| October 14 – November 15
|
Ovche Pole Offensive, a phase of the Central Powers invasion of Serbia, Bulgarians break through Serbian lines.
|
|
| October 15
|
The United Kingdom declares war on Bulgaria.
|
|
| October 16
|
France declares war on Bulgaria.
|
|
| October 17 – November 21
|
Battle of Krivolak, start of the set up of the Salonika Front.
|
|
| October 18 – November 4
|
Third Battle of the Isonzo
|
Details
|
| October 19
|
Italy and Russia declare war on Bulgaria.
|
|
| October 27
|
A French army lands in Salonika and, with the help of British and Italian troops, sets up a Balkan Front.
|
|
