The entire membership of the National Guard was drafted into federal service for World War I. After war was declared in April 1917, National Guard units were first called into federal service by President Wilson under the militia clause of the Constitution. Most of these units mobilized at their local armories or in state military camps, and they began actively recruiting up to full wartime strength while conducting local patrols to defend against suspected German saboteurs. Guardsmen could not be deployed overseas as militia, however, since the Constitution stipulated that the militia could only be used to “execute the laws of the Union, suppress insurrection, and repel invasions.” To circumvent this restriction, the Army’s Judge Advocate General determined that it would be necessary to draft each Guardsman into federal service, thus severing his ties to the state militia and freeing him for service overseas. Just over 379,000 Guardsmen were drafted on August 5, 1917, more than doubling the size of the U.S. Army with the stroke of a pen. Despite the fact that the military would swell to over 4 million men during the war, the brunt of the fighting in the trenches in France would be borne by the Guard. All 18 Guard divisions served overseas as part of the 43 division American Expeditionary Forces; 12 of the 29 divisions that saw combat were from the Guard (the rest of the divisions were broken up and the men used as replacements).