Did the Allies or the Central Powers built the first trenches?

Explanation:

In the wake of the Battle of the Marne—during which Allied troops halted the steady German push through Belgium and France that had proceeded over the first month of World War I—a conflict both sides had expected to be short and decisive turns longer and bloodier, as Allied and German forces begin digging the first trenches on the Western Front on September 15, 1914.

ok so u have2 basically