Ludwig Quidde (March 23, 1858 - March 4, 1941), the oldest son of a wealthy merchant, grew up in the republican atmosphere of the Hanseatic city of Bremen, enjoying an unusually liberal education at its humanistic gymnasium, «an education in freedom to freedom». He studied at the Universities of Strassburg and Gottingen, where his professors recognized and furthered his aptitude for historical research.

Under the sponsorship of Professor Weizsacker in Gottingen, Quidde was given a post on a board of editors responsible for the publication of the medieval German Reichstag documents, a post he held until 1933 when the Bavarian Historical Commission removed him for political reasons. In 1889 he founded the Deutsche Zeitschrift für Geschichtswissenschaft [German Review of Historical Sciences], a journal which he edited until 1896; from 1890 to 1892, he was on the staff of the Prussian Historical Institute in Rome. Quidde, however, did not follow a career as a professional historian, perhaps because he had a substantial private fortune, but he always maintained a lively interest in history, especially constitutional history, even after his attention had turned from the academic to the political.

The publication of the pamphlet Caligula: A Study of Imperial Insanity in 1894 changed the course of Quidde's career. Seemingly an objective study of the Roman emperor Caligula, emphasizing his madness, his pleasure in sham heroics, his ruthless use of power, his vanity as an actor and conceit as an orator, the pamphlet was, in fact, a satire on Emperor Wilhelm II and the «Byzantine» nature of the Prussian society of which he was a part. Quidde escaped conviction of the charge of lese majesty: he denied that he had intended to draw an analogy between the two emperors, thus leaving to the prosecution the task of proving the validity of the analogy, an alternative too embarrassing to accept.

Quidde entered politics in Munich. In 1895 he helped to reorganize the German People's Party which was, in political philosophy, anti-prussian and antimilitary; in 1902 he won a seat on the City Council of Munich; from 1907 to 1919 he served in the Bavarian Assembly; in 1919 he was elected to the Weimar National Assembly.

Quidde's political ideology was a direct heritage from the Enlightenment. Uncompromisingly ethical, he strove to imbue the German people with a sense of justice which would of itself generate social reform. He had the courage of his convictions. After delivering a political speech on January 20, 1896, Quidde was accused of lese majesty, tried, and sentenced to three months in the Munich prison Stadelheim. For writing an article in 1924 attacking secret military training, he was arrested, found guilty of «collaborating with the enemy», and put in prison for a brief period.

Initially not antiwar on principle, Quidde's interest in the peace movement, prompting him to join the German Peace Society shortly after its founding in 1892, grew out of his historical studies, his ethical ideals, his distrust of the military, and the urgings of his wife, Margarethe, whom he married in 1882. He filled a position on the Council of the International Peace Bureau in Bern, rose to a position of leadership in the World Peace Congress in Glasgow in 1901, joined with Frédéric Passy at the Congress at Lucerne in 1905 to achieve a rapprochement between German and French, supervised the organization of the World Peace Congress of 1907 in Munich, became president of the German Peace Society in 1914, a position he held for fifteen years.

When World War I broke out, Quidde went to The Hague, attempting to maintain ties with English and French peace groups. The attempt failed, and when Quidde returned to Germany he was charged with treason, though the charges were later dropped. Nonetheless, Quidde was kept under surveillance for months, his mail censored, and his pamphlets confiscated. At the end of the war, Quidde continued to pull together the remnants of the German peace movement, heading the German Peace Cartel, a body composed of twenty-one organizations.

When Hitler came to power, Quidde fled first to Munich and then to Geneva, where he lived from March, 1933, until his death in March, 1941. Although Quidde's private fortune had been wiped out by the inflation, he was able to live fairly well with the help of friends and with a subvention from the Nobel Peace Prize Committee for his projected book, German Pacifism during the World War, which was never finished. Even in exile, Quidde continued to attend World Peace Congresses, to publish articles, and to exercise his organizational talents by founding the Comité de secours aux pacifistes exilés to care for fellow political exiles from Nazi Germany.