In August 1914 the unit was part of the 2nd Division of the Königsberg-based I Corps. With the Russian invasion of East Prussia in August 1914, the unit saw action during the prelude to the Battle of Tannenberg. The 33rd Fusiliers charged the Russian-occupied village of Mallwischken near Gumbinnen and cleared the area. Later as the battle for East Prussia developed, the regiment occupied high ground near the village of Usdau.