With the outbreak of the First World War and the formation in July 1914 of the units of the Vilnius District of the 1st Army (Russian Empire), Captain Wilhelm Garf took over the position of senior adjutant of the Quartermaster General of Staff. As part of the Northwestern Front, the 1st Army (Russian Empire), under the command of General Paul von Rennenkampf, entered East Prussia on August 4, 1914. Already in the first weeks of the war, William Garf distinguished himself in the Battle of Gumbinnen. On December 6, 1914, he was awarded the rank of lieutenant colonel, and in February of the following year he was appointed senior adjutant to the commander of the 26th Infantry Division (commander - Major General P. A. Tikhonovich). The division was part of the 2nd Army Corps (Russian Empire), which since August 8 has been part of the 1st Army (Russian Empire). In February, the division advanced to Poland, where V.E. Garf distinguished himself in fierce battles in the area of the town of Sejny (02.25.02.1915), the settlement of Krasnopol (03.15.1915), and the city of Suwalki.