Completing her training, Baer began her career as a teacher in Hamburg. During
World War I Baer relocated to
Munich and became involved with Heymann,
Anita Augspurg and
Helene Stöcker in the
Pacifist Movement. In 1915, she attended
International Congress of Women held in
The Hague, where the first ideas were launched for women to form the International Committee of Women for Permanent Peace. That meeting was followed-up in 1919 with the formation of the
Women's International League for Peace and Freedom (WILPF), which Baer immediately joined, served in various positions with the German branch of WILPF from its founding year. Between 1918 and 1919, Baer set up a women's council in the Munich Ministry of Social Affairs, for the newly created
Bavarian Soviet Republic. She also participated in the summer courses on
Internationalism, sponsored by WILPF in the early 1920s. Between 1919 and 1933, she worked for the women’s journals
Die Frau im Staat (The Woman in the State) and
Die Friedenswarte (Peace Watch). In 1922, Baer, who had been executive secretary of the German WILPF for a year, made her first trip to the United States. She missed her meeting with
President Harding, when immigration detained her because of her membership in the
Communist Party of Germany and fears that she had insufficient funds to support herself while in the country. Released after the intervention of
Jane Addams, Baer, when speaking at a later meeting, urged women to join in the peace movement and anti-war demonstrations. Giving lectures with members from Britain and France, Baer urged the United States to withdraw troops from
Latin America, to release political prisoners, and to recognize the
Soviet Union. Along with Heymann and
Frida Perlen, Baer led the efforts to reconcile German and French women in the
interwar period. One such initiative was a tree planting held in 1926 in northern France. Baer also served as vice president of the German Peace Cartel and traveled widely in Europe. Returning to the United States in 1924 to attend the WILPF International Conference, Baer urged that
Hitler be taken as a serious threat. In 1929, she succeeded Jane Addams as the International Chair of the WILPF, but due to the volume of work to be done, it was decided that the responsibilities Addams had carried were to be shared with
Emily Greene Balch and
Clara Ragaz. When Hitler took over Germany in 1933, Baer fled the country and obtained citizenship in
Czechoslovakia. WILPF leadership called an emergency meeting and gave her
asylum, hiring her to work full-time to prepare for their next conference. When the
Nazis seized and
occupied the country, she then fled to
Geneva. Upon Addams death in 1935, it was decided to have Baer, Ragaz and
Cornelia Ramondt-Hirschmann, continue the shared responsibilities as WILPF chairs. Making her third trip to the United States that year, Baer participated in a disarmament conference, appealing for the nations of the world to work together for peace. In 1939, Baer, the monitor for WILPF of the Economic Council of the
League of Nations, was sent to the United States. The Council had been moved to
Princeton, New Jersey and it was deemed necessary for Baer to relocate for safety concerns. From there, she served as the primary leader of the WILPF, throughout the war, preparing the circular communications that quarterly were sent to international branches. The chair was still shared by Baer and Ragaz, but British pacifist
Kathleen Innes, had replaced Ramondt-Hirschmann in 1937 as the third member. The three women sent a letter to
President Roosevelt urging him to allow refugees into the country. In 1940, Baer became American citizen, though she returned to Geneva permanently in 1950. Having kept alive the contacts and the organization, at the end of the war, Baer became the first WILPF consultant to the
United Nations and held that post until 1972. Some of the initiatives she was involved in were urging the
World Health Organization to investigate what effect
atomic tests and specifically
radiation posed to the population. Beginning in 1955, she stressed the need to utilize
solar energy, rather than pursue
nuclear power, and in a 1960 campaign urged rural education through radio broadcasting. In 1965, at the fiftieth anniversary convention for the creation of WILPF, Baer expressed her frustration that the organization had moved away from its feminist roots, reminding members that until full equality in all spheres of life had been attained, women would remain at risk. The following year, as an observer to the UN NGO Forum held in Rome, Baer again spoke about the links between feminism and pacifism, while urging self-determination for
Viet Nam. At the close of the 1960s, Baer was still committed to the organization, pressing for membership to be expanded to include young people and those outside mainstream organizations. She pressed for disarmament and worked to get the superpowers to agree to passage of the 1968
Nuclear Non-Proliferation Treaty. Ahead of her time in many ways, Baer's ideas preceded both
second-wave feminism and the 1980s rebirth of the peace movement. In 1977, a documentary film by Michaela Belger, entitled
Gertrud Baer. Ein Leben für die Gleichberechtigung der Frau, für Frieden und Freiheit (
Gertrud Baer: A Life for the Equal Rights of Woman, for Peace and Freedom) was released to honor Baer's work. ==Death and legacy==