Army Day should not be confused the Army's Birthday, which is celebrated on June 14. The origins of Army Day can be traced back to a little-known Defense Test Day, which was observed only twice: once in 1924 and once in 1925. Congress then disallowed any further observances of this day. In response, the Military Order of the World War under Colonel Thatcher Luquer established Army Day. Army Day was first celebrated on May 1, 1928. That date was chosen in hopes of dampening Communists' celebration of Workers' Day, which also occurs on May 1. But, starting in 1929, Army Day was changed to April 6, the anniversary date of the United States' entry into World War I.
Army Day was established as a nationwide observance to draw public attention to national defense and to acquaint the public with Army activities. In addition, the day was used to stress the need for military preparedness, which the nation had lacked as it entered earlier major conflicts. "The failure to make adequate preparation for the inevitable struggle, the consequent suffering from disease and death entailed upon the armies which were hastily raised, the prolongation of the conflict far beyond the time which sufficient and equipped forces would have required for victory, and the heavy costs of reconstruction" were caused by the lack of preparation of the nation.
On April 4, 1936, President Roosevelt issued a proclamation that Army Day be recognized by Congress as April 6 and observed nationwide. On March 1, 1937, Congress passed Resolution #5-75 which officially recognized Army Day.
Army Day was last observed nationally on April 6, 1949.