The 'Fourth Enemy Offensive' was the Yugoslav designation for the Axis undertaking, also known to the Yugoslavs as the Battle of the Neretva and the Germans as 'Weiss' (ii), against the partisan forces of Josip Broz Tito in the area between western Bosnia and northern Herzegovina in German-occupied Yugoslavia, and culminating in the partisan retreat over the Neretva river (January/April 1943).