What law allowed the govenment censor the soldiers letters?

The law that allowed the government to censor soldiers' letters during wartime is known as the Espionage Act of 1917. This act was enacted to prevent the dissemination of information that could harm national security, particularly during World War I. It authorized the government to censor communications, including letters sent by soldiers, to ensure that sensitive information did not reach enemy hands. Subsequent amendments and related legislation further expanded these censorship powers during later conflicts.