On February 1, 1937, the wave of sit-down strikes against General Motors broadened when Chevrolet Plant No. 4 was seized. The United Auto Workers’ strategy used a diversionary strike at nearby Plant No. 9 to draw company personnel there while the true target, Plant No. 4, was secured. As unionists and company guards battled inside Plant No. 9, other strikers captured the key Plant No. 4. Pickets outside were aided by the Women’s Emergency Brigade, which fended off police until strikers inside secured the vital plant. Because all Chevrolet engines were produced in Plant No. 4, cutting off this supply would close Chevrolet operations nationwide. On February 11, 1937, the strike ended when General Motors recognized the UAW as bargaining agent for its members, in one of the most significant events in labor history.