At the outbreak of World War I, 80% of the German army (consisting in the West of seven field armies) was deployed in the west according to the plan Aufmarsch II West. However, they were then assigned the operation of the retired deployment plan Aufmarsch I West, also known as the Schlieffen Plan. This would march German armies through northern Belgium and into France, in an attempt to encircle the French army and then breach the 'second defensive area' of the fortresses of Verdun and Paris and the Marne river.
Middle Eastern theatre
During World War I, the Eastern Front was a theatre of operations that encompassed at its greatest extent the entire frontier between the Russian Empire and Romania on one side and the Austro-Hungarian Empire, Bulgaria, Turkey and Germany on the other. It stretched from the Baltic Sea in the north to the Black Sea in the south, included most of Eastern Europe and stretched deep into Central Europe as well. The term contrasts with "Western Front", which was being fought in Belgium and France.