The entry of the United States into the World War greatly accelerated the farm bureau movement. "Food will win the war" was the slogan which challenged American agriculture. The number of county agents in the North and West increased from 542 to 1,133 within the year ending June 30, 1918. It was the county agent system which formed the mechanism through which the federal government secured the whole-souled cooperation of the farmers of the United States under peculiarly trying conditions. The winter of 1917-18 was severe and seed corn was unusually poor. As a result, the available supply of sound seed corn in the spring of 1918 was the lowest on record in the face of the greatest need for a bumper crop. Had it not been for the remarkable organization developed through the county agents and the farm bureau system of the entire country, the corn crop of the great Corn Belt would have been far below normal. As it was, nearly a normal acreage was planted and an abundant harvest secured. The role which the agriculture of the United States played in the World War has never been adequately written or appreciated, but it was full of as much romance and heroism as were the industries which commanded the headlines of the press. Dr. Bradford Knapp, for many years in charge of the county agent work in the Southern States after the death of his father, its founder, has called attention to the fact that during the war "of the four great activities or industries in America, agriculture, manufacturing, mining, and transportation,--one alone--agriculture, stood the test, and that mainly because there was already in existence an organization extending from the United States Department of Agriculture through every state agricultural college ... to the counties and the farmers, by which information was rapidly disseminated and farmers were made aware of conditions of what must be done to win the war." It was inevitable that such an organization growing rapidly during a war should develop an unusual solidarity, and this was but strengthened by the difficulties which agriculture encountered with the cessation of hostilities. During the war several states had formed state federations of the county farm bureau associations and in November, 1919, a convention was called at Chicago for the formation of a national organization, which resulted in the formal organization of the American Farm Bureau Federation[48] in March, 1920, with 28 states represented, and a membership in county farm bureaus of 400,000. In the next two years the southern states, which previously had developed no strong county organizations, rapidly adopted the farm bureau idea, and when the American Farm Bureau Federation held its second annual meeting at Atlanta, Ga., in November, 1921, it included 35 states with a local membership of 967,279.