Expansionism, border disputes, and political upheaval on a global scale marked the 1930s. Germany invaded Poland in September 1939. A few days later, Great Britain declared war on Germany.
In December 1941 Japan executed attacks throughout Asia and the Pacific, continuing an expansionism that had begun with Japanese occupations in Korea and China in 1930. These events and others launched a second global war.
Most of the nations involved quickly initiated stringent censorship that affected newspapers, radio broadcasts, telegraph messages, and mail. Censorship of both military and civilian mail was deemed necessary to prevent dissemination of sensitive information across enemy lines. Trained civilians or military officers conducted the censorship. They opened, screened, and, if necessary, blacken or cut away questionable portions of the written communications. The letter would be resealed and marked with an examiner or censor handstamp.