[3] During the World War I, Schirrmann served in a regiment holding a position on the Bernhardstein, one of the Vosges Mountains – separated from the French troops by a narrow No man's land, which he described as "strewn with shattered trees, the ground ploughed up by shellfire, a wilderness of earth, tree-roots and tattered uniforms".

German and French troops spontaneously made peace and ceased hostilities; they visited each other through disused trench tunnels, and exchanged wine, cognac, and cigarettes for Westphalian black bread, biscuits, and ham.

"[4] Military discipline was soon restored, but Schirrmann pondered over the incident wondering whether "thoughtful young people of all countries could be provided with suitable meeting places where they could get to know each other".

[2] After World War II, he played a key role in rebuilding the German association, and was recognized the Order of Merit of the Federal Republic of Germany (Bundesverdienstkreuz) in 1952.

[2] In 1946, he was flown to the International Youth Hostel Conference in Scotland by an American friend on a private plane, making him the first German civilian to enter British territory after World War II.