On 2 August 1914, at the outbreak of the First World War, Prittwitz was appointed commander of the
Eighth Army and assigned to defend
East Prussia from an expected
Russian attack. When the unexpectedly swift
Russian invasion gained early success in the
Battle of Gumbinnen (20 August 1914) and threatened his rear, Prittwitz suggested a retreat to the west of the
Vistula. This would have meant abandoning East Prussia, an action which the
German General Staff found unacceptable. Additionally, commander of the I Corps
Hermann von François complained to the General Staff that his superior was panicking; the General Staff concurred in this assessment. On 23 August 1914
Moltke the Younger promptly appointed
Paul von Hindenburg to replace Prittwitz as Eighth Army commander. Hindenburg, along with
Erich Ludendorff as replacement for Chief of Staff
Georg von Waldersee, then successively destroyed the two invading Russian armies at the Battles of
Tannenberg (23–30 August 1914) and the
Masurian Lakes (2–16 September 1914). Prittwitz retired to
Berlin, where he lived for three years before dying of a
heart attack. He was buried in the
Invalids' Cemetery (
Invalidenfriedhof) in Berlin. ==Honours and awards==