Cartier-Bresson also studied cinematography in New York in 1935 at Nykino, short for "New York Kino", the cooperative led by Paul Strand. He subsequently assisted Jean Renoir on his films and made his own documentary in 1937. His commitment to photojournalism began that same year with photographs of the coronation of Queen Elizabeth and King George VI. In 1940, Cartier-Bresson was drafted into the French Army's Film and Photography Unit. German soldiers captured him that year, and he spent the next thirty-five months imprisoned. After escaping, he began working for the French Resistance, photographing the occupation of France and its subsequent liberation.
 
In 1947 he co-founded Magnum Photos with Robert Capa, David Seymour, William Vandivert and George Rodger. He arrived in India that autumn to cover the newly independent and recently partitioned nation. The following year he was granted permission to photograph Gandhi, producing a series of candid, unobtrusive images without flash, including photographs taken just an hour before his assassination. He also covered Gandhi's funeral and the aftermath of his murder. Images of Gandhi's body surrounded by mourners, Jawaharlal Nehru's address to the nation and public gatherings filling the streets were published in Life magazine, bringing Cartier-Bresson international recognition.