 When the Chicago Great Western was federalized during World War I , a contingent of Illinois National Guardsmen were assigned to protect the tunnel . 
 When the Chicago Great Western was federalized during World War I , a contingent of Illinois National Guardsmen <a href='uninflect' title='1'><mark>were</mark></a> assigned to protect the tunnel . 
When the Chicago Great Western was federalized during World War I , a contingent of Illinois National Guardsmen was assigned to protect da tunnel .