If you except Austria, war started without any clear direct motive.

Austria felt Serbia was a threat to it’s integrity and declared war to this country, Russia wanted it’s influence to be preserver over Slavic countries and mobilized, German considered that Russia’s mobilization was an act of war, that war with Russia meant war with France and declared war to both these countries, Britain did not want to see the German fleet in Belgium’s harbours.

Thus, the goals of war were very imprecise, the countries being at war mostly because other countries were at war or were preparing to it.

Those goals, being imprecise, were completely dependant on military situation and it’s evolutions.

As time passed and that body count grew, limiting the war objectives to a few territorial gains became impossible.

This made peace very difficult as no camp could fix conditions that could make the end of war acceptable to it’s own opinion and reliable to other countries involved.

The allies could hope a military victory in 1915 and in 1917, central powers could hope it in 1916, 1917 and early 1918 at least on one of the fronts, whether eastern or western.

So all along the war, peace never appeared as a reliable option even when Wilson attempted to present himself as a referee.

Moreover, the simple fact of making peace proposals was very dangerous as it would necessary have meant a diminution of fighting spirit.

I think it is possible to say that war became too big to be stopped by anything but itself.