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The Allies had had time to consider the problem. The French being brought around to agree that the key to the defence was the Malakoff.:441 Emphasis of the siege at Sevastopol shifted to the British left, against the fortifications on Malakoff hill.:339 In March, there was fighting by the French over a new fort being built by the Russians at Mamelon, located on a hill in front of the Malakoff. Several weeks of fighting saw little change in the front line, and the Mamelon remained in Russian hands.

Where was the Russians building a new fort?
Mamelon