German and Russian troops had stared at one another for almost a month from their trenches in front of Lötzen, where Fort Boyen held up the Russian First Army. When the Germans went on the offensive, they faced a much more extensive network of trenches and a greater concentration of artillery than anywhere else on the front. Given a chance to redeem himself for his poor behavior at Ortelsburg, Lt. Gen. Otto Hennig of 35th Infantry Division sent his men forward in a brutal frontal assault against well-prepared defenders.

The Russians had prepared themselves for just such an attack, and backed their front-line position with additional artillery attached from corps and army assets. After a day of furious fighting including many hand-to-hand engagements with cold steel, Hennig's division finally broke through. This would be the most intense example of trench fighting during the East Prussian campaign, and it resulted in heavy casualties for both sides before the Russian II Corps gave way and the First Army's left flank crumbled.