On June 12, 1915, a gas attack took place in this area. The breach that German units made that day was 6 km wide and 600 to 3,000 meters deep, so it was not a spectacular success. According to the "Bojowy Journal", about 1,700 prisoners were taken prisoner and about 2,000 more died from gas or were killed in combat. According to Russian sources, 3,100 Russian soldiers were poisoned on June 12, 1,200 of those fatally poisoned remained in the trenches. German losses amounted to 1,200 soldiers killed and wounded, in addition to 350 soldiers were poisoned by gas.
Some of the soldiers killed in this battle were buried in the cemetery in Kozłów I. This cemetery was rebuilt in the 1920s. Those who died originally in Zakrzew were also buried here. Tombstones excavated from the ground indicate that soldiers buried in the cemetery include those from the 8th Reserve Infantry Regiment and the 175th Infantry Regiment.