The key instrument of this campaign was the so-called Sullivan Principles, authored by and named after the Rev. Dr. Leon Sullivan. Leon Sullivan was an African-American preacher in Philadelphia who, in 1977, was also a board member of the corporate giant General Motors. At that time, General Motors was the largest employer of Blacks in South Africa. The principles required that the corporation ensure that all employees are treated equally and in an integrated environment, both in and outside the workplace, and regardless of race, as a condition of doing business. These principles directly conflicted with the mandated racial discrimination and segregation policies of apartheid-era South Africa, thus making it impossible for businesses adopting the Sullivan Principles to continue doing business there.