Born in Baden-Baden into a Jewish family, his parents were cellist Bernhard Cossmann and his wife Mathilde Hilb, the daughter of a Karlsruhe merchant.
During World War I, he intransigently promoted victory for Germany, while the magazine's special editions propelled its circulation upward, both on the front and among civilians.
[1] Cossmann's tireless struggle against the Treaty of Versailles and campaigns about the related topics of war debt (1922) and the stab-in-the-back myth (1925) earned him the reputation of a ruthless nationalism.
He was falsely accused of pursuing causes on behalf of a political party or wealthy backers, but in fact Cossmann acted from conviction.
While a fanatic when it came to his version of the truth, he was reportedly an unusually kind man possessed of warm social feeling, as well as a tireless promoter of charitable initiatives.