The opening phase of the Great War was long in the planning. The German General Staff under Alfred von Schlieffen interpreted the Anglo-French entente of 1904 as a possible threat. Further, if Russia were to be drawn in to the alliance as well, then Germany would face the prospect of a two-front conflict.
The German war plan, often called the Schlieffen Plan, provided for the following actions in the event of war with France:
An immediate and powerful strike against France was to be the first order of business. The German move was planned to pass through the neutral nations of Belgium, Luxembourg, and the Netherlands, in order to avoid the heavily defended Franco-German border.
Time was of the essence; the Germans anticipated knocking France out of the conflict before the Russians could mobilize a period judged to be about six weeks.
At the commencement of military activity, the Germans planned to take control of the English Channel coast to deny the British the opportunity to come to French aid.
An initial holding action was anticipated on the Eastern Front. The Germans planned to employ the great bulk of their force against France, then rapidly transfer them against the Russians after the victory in the west.
One modification was made to the Schlieffen Plan prior to the outbreak of war. It was decided that the Netherlands should be spared and the brunt of the invasion of France should come through Belgium. The route was more direct through Belgium and such an invasion would disrupt one neutral nation, not two.
The Schlieffen Plan was implemented on April 4, 1914, when German forces stormed into Belgium. Much to their amazement, the Belgians mounted an inspired defense. The carefully crafted timetable could not be honored and the frustrated Germans treated the Belgians with great brutality. German actions were widely reported in the press; a body of anti-German sentiment began to grow in the United States.
The Germans were further thrown off stride by the Russians' ability to act. Russian armies were quickly put into the field and began an advance against German soil. The Battle of Tannenburg (August 26-30, 1914), while a costly defeat for Russia, did force Germany to withdraw western soldiers for the campaign in East Prussia.
The Russians, by honoring their treaty obligations to France, helped to establish a stalemate on the Western Front. A protracted period of trench warfare ensued.