In the United States, August Vollmer introduced other reforms, including education requirements for police officers. O.W. Wilson, a student of Vollmer, helped reduce corruption and introduce professionalism in Wichita, Kansas, and later in the Chicago Police Department. Strategies employed by O.W. Wilson included rotating officers from community to community to reduce their vulnerability to corruption, establishing of a non-partisan police board to help govern the police force, a strict merit system for promotions within the department, and an aggressive recruiting drive with higher police salaries to attract professionally qualified officers. During the professionalism era of policing, law enforcement agencies concentrated on dealing with felonies and other serious crime, rather than broader focus on crime prevention.