Why a 1909 European war is less advanced and more painful

How does the First World War change if it begins in 1909?

The naval balance is closer, Allied armies are less ready and submarine warfare is much less mature, producing a different but still severe conflict.

An earlier war finds Britain and Germany much closer in dreadnought strength, forcing pre-dreadnoughts into a more important place in the battle line. The French army is less prepared, while the British Expeditionary Force is trained mainly for imperial policing rather than continental mass war. Another desperate defence near Paris could lead to a conflict that is technologically less advanced but potentially even more painful. Submarine development loses five crucial years, so the commerce war may not take the form familiar from 1914-18.