The Schlieffen Plan was an attack plan. It was formulated Germany, but it wasn’t put into action until troops from Russia were mobilized along the border of Germany, attacking Germany. The attack was meant to put France on the spot and take down the country that top lieutenants had identified as Germany’s biggest threat in Europe. The idea was to go through Belgium, a country that Britain had promised to support in neutrality. The entire plan hinged on two things: Russia attacking Germany with less superior weapons, and Britain not supporting Belgium’s decision to stay neutral.
Needless to say, that didn’t happen. As tensions continued to increase due to Germany’s expanding power, the Schlieffen Plan almost worked. However, a single battle with poor communication - the first Battle of the Marne - took Germany’s plan and crumbled it to pieces.