This article is about the United States campaigns in World War I. American entry into World War I in early April 1917 resulted in the American Expeditionary Force (AEF) on the Western Front, under General John J. Pershing, being engaged in 13 campaigns, during the period 1917–18, for which campaign streamers were designated. The streamer uses the colors of the World War I Victory Medal ribbon which had a red center with a rainbow on each side of the center stripe and a purple edge. The double rainbow symbolizes the dawn of a new era and the calm which follows the storm.
The details above and following are taken from "The Army Flag and Its Streamers", a pamphlet which was originally prepared in 1964 by the Office of the Chief of Military History, in cooperation with the Office of the Chief of Information and the U.S. Army Exhibit Unit, to provide general summaries of each of the campaign ribbons authorized to be displayed on the Army flag. It was subsequently updated by the Center of Military History to add the campaigns from Vietnam.
The year the United States entered World War I was marked by near disaster for the Allies on all the European fronts. A French offensive in April, with which the British cooperated, was a failure, and was followed by widespread mutinies in the French armies. The British maintained strong pressure on their front throughout the year; but British attacks at Messines Ridge (7 June), at Passchendaele (31 July), and at Cambrai (20 November) failed in their main objective–the capture of German submarine bases–and took a severe toll of British fighting strength. Three American engineer regiments–the 11th, 12th, and 14th–were engaged in construction activity behind the British lines at Cambrai in November, when they were unexpectedly called upon to go into the front lines during an emergency. They thus became the first AEF units to meet the enemy.