The Battle of the Lys (7–29 April 1918) also known as the Lys Offensive, the Fourth Battle of Ypres, the Third Battle of Flanders, Operation Georgette, Portuguese: Batalha de La Lys and French: 3ème Bataille des Flandres, was part of the 1918 German offensive in Flanders during World War I, also known as the Spring Offensive.