Spring Offensive

The 1918 Spring Offensive or Kaiserschlacht ("Kaiser's Battle"), also known as the Ludendorff Offensive, was a series of German attacks along the Western Front during World War I, which marked the deepest advances by either side since 1914. The German authorities had realised that their only remaining chance of victory was to defeat the Allies before the overwhelming human and matériel resources of the United States could be deployed. They also had the advantage of nearly 50 divisions freed by the Russian surrender (Treaty of Brest-Litovsk). 
The first and most important part was called Operation Michael. It used new infiltration tactics. After the offensive, not enough German soldiers were still alive to win the war anymore.