What battle lasted for 4 months in the World War 1?

The Battle of Verdun, fought from February 21 to December 18, 1916, lasted for nearly 11 months but is often remembered for its intense and prolonged fighting. However, the Battle of the Somme, which began on July 1, 1916, and continued until November 18 of the same year, is another significant engagement that lasted for approximately four months. Both battles symbolized the brutal and attritional nature of World War I.