In March, the German offensive was extended to the left (west) bank of the Meuse, to gain observation of the ground from which French artillery had been firing over the river onto the Meuse Heights. The Germans were able to advance at first but French reinforcements contained the attacks short of their objectives. In early May, the Germans changed tactics and made local attacks and counter-attacks, which gave the French an opportunity to begin an attack against Fort Douaumont. Part of the fort was occupied, until a German counter-attack recaptured the fort and took numerous prisoners. The Germans changed tactics again, alternating their attacks on both banks of the Meuse and in June captured Fort Vaux. The Germans continued the offensive beyond Vaux, towards the last geographical objectives of the original plan, at Fleury-devant-Douaumont and Fort Souville. The Germans drove a salient into the French defences, captured Fleury and came within 4 km (2.5 mi) of the Verdun citadel.
In July 1916, the German offensive was reduced to provide artillery and infantry reinforcements for the Somme front and during local operations, the village of Fleury changed hands sixteen times from 23 June to 17 August. A German attempt to capture Fort Souville in early July was repulsed by artillery and small-arms fire. To supply reinforcements for the Somme front, the German offensive was reduced further and attempts were made to deceive the French into expecting more attacks, to keep French reinforcements away from the Somme. In August and December, French counter-offensives recaptured much of the ground lost on the east bank and recovered Fort Douaumont and Fort Vaux.
The Battle of Verdun lasted for 303 days and became the longest and one of the most costly battles in human history. An estimate in 2000 found a total of 714,231 casualties, 377,231 French and 337,000 German, for an average of 70,000 casualties a month; other recent estimates increase the number of casualties to 976,000, during the battle, with 1,250,000 suffered at Verdun during the war.