Fighting between the Poles and the Germans resumes only in 1017 after the failure of peace talks.

Henry marches an army from Leitzkau to Głogów (Glogau), where Boleslaw I awaits him, but chooses not to besiege the city as it is too strongly fortified.

Instead, Henry besieges nearby Niemcza (Nemzi, Nimptsch); however, Polish reinforcements manage to enter the city on two occasions and the siege is without success.

At the same time, Mieszko goes to Moravia at the head of ten legions and plans an allied attack together with Bohemia against the Emperor.

The contemporary German chronicler Thietmar of Merseburg, generally ill disposed towards Poles, on this occasion comments on the bravery and skill of the defenders at Niemcza, noting that they neither cheered when they were successful, nor lamented when they suffered a setback.

The inhabitants of the city also erect a cross on the wall that faces the pagan Lutician allies of the emperor.

Eventually, due to an illness of part of his army, Henry aborts the siege and withdraws, taking the route to Bohemia because the way back into Germany is blocked by Boleslaw's main forces, stationed at Wroclaw.