In March 1916, Villa and a small group of men attacked the city of Columbus, NM. The Battle of Columbus resulted in civilian casualties and prompted the U.S., to send General John J. Pershing on a Punitive Mission, which was unsuccessful in its attempt to capture Villa. Sommerfeld, who had proposed to the German government in May 1915 that he could create an incident which would provoke a war between the U.S. and Mexico, became a prime suspect in Villa's attack on Columbus. However, no investigator or historian has been able to prove Sommerfeld's involvement.