Ostangriff

Ostangriff, or 'Eastern Attack', was the plan devised by Helmuth von Moltke the Younger, as a revised version of the outdated 1905 Schlieffen Plan.

Initial Planning
The main difference between the two plans was that the old Schlieffen Plan focused on defeating France first, and quickly, before turning their forces on Russia. Von Moltke, however, saw the significant improvements in Russian infastructure and armaments since 1905. German High Command estimated that Russia would be fully prepared for war in 1917, which is why the High Command decided to attack in 1914. Moltke hoped to capitalize on internal instablility and outdated armament to descisively defeat the Russians, while the German Army could shore up behind the Rhein River. On the 3rd of August, the plan was officialy adopted.

Effectiveness
In the early days of the war, the plan seemed to be successful. The invasion of East Prussia was repulsed at high cost in the Battle of Königsberg, followed up in the Battle of Masurian Lakes and Tannenberg. However, the Brusilov Line interrupted the 'quick victory' hoped for. Eventually, with the collapse of the Second Rheinish Offensive, the Brusilov Line broke, and the August Revolution eventually caused Russian withdrawl, and eventually the German victory in the Weltkrieg.

Aftermath
Whether or not the Ostangriff was necessary continues to be a hotly debated topic. Some say that the Russian failures in invading Eastern Prussia is in itself proof that 'Eastern Attack' was not necessary, and that an invasion of France could have succeeded while Russia collapsed could have resulted in a German victory on the continent in 1915 or 1916. Others say that an increased German presence in the East was what led to the German victories in Königsberg, Tannenberg, and Masurian Lakes.