Maria Montessori visited the United States, where she was warmly received and lectured on her educational methods. Her visit further boosted the popularity of the Montessori Method in America.

Montessori began offering international training courses for teachers, attracting educators from around the world. These courses were essential for disseminating her educational philosophy and methods accurately.

World War I disrupted the spread of Montessori education, although schools continued to operate in various countries. The war also prompted reflection on the role of education in promoting peace and understanding.

She established a Montessori training center in London, further consolidating her influence in Europe. The London center became a hub for Montessori education and research.

Maria Montessori founded the Association Montessori Internationale (AMI) to safeguard the integrity of the Montessori Method and to ensure the proper training of teachers. AMI remains the leading authority on Montessori education worldwide.

With the rise of Fascism in Italy under Benito Mussolini, Montessori's relationship with the Italian government became strained. Her emphasis on freedom and individual development clashed with the authoritarian ideology of the regime.