Two months after the outbreak of World War I, he was made captain of the
battlecruiser , which he also commanded during the
Battle of Dogger Bank. In September 1915, he became
commodore and
commanding officer of the
Fourth Scouting Group of five light cruisers (, , , , ), leading the group during the
Battle of Jutland. Promoted to
Konteradmiral in November 1916, he was placed in command of the Second Reconnaissance Group, a fleet of six light cruisers including his flagship . He commanded the group during the mine sweeping operation that led to the
Second Battle of Heligoland Bight in November 1917. Faced with a surprise attack by a numerically superior force of British ships, he successfully withdrew his group under fire to the protection of the battleships and . Reuter was vilified in Britain and made a
prisoner of war, along with the other 1,773 officers and men of the fleet's remaining rump crews. In Germany, he was celebrated as a hero who had protected the honour of the navy. While most of the imprisoned Germans were soon returned to Germany, Reuter was among several who remained imprisoned in Britain. He was eventually released and finally returned to Germany in late January 1920. == Later life ==