George Wallace, one of the most controversial politicians in U.S. history, was elected governor of Alabama in 1962 under an ultra-segregationist platform. When African-American students Vivian Malone and James Hood attempted to desegregate the University of Alabama in June 1963, Wallace, flanked by state troopers, literally blocked the door of the enrollment office. The U.S. Supreme Court, however, had declared segregation unconstitutional in 1954′s Brown v. Board of Education, and the executive branch undertook aggressive tactics to enforce the ruling.

On June 10, 1963, President John F. Kennedy federalized National Guard troops and deployed them to the University to force its desegregation. The next day, Governor Wallace yielded to the federal pressure, and Malone and Hood successfully enrolled. In September of the same year, Wallace again attempted to block the desegregation of an Alabama public school, this time Tuskegee High School in Huntsville. President Kennedy once again employed his executive authority and federalized National Guard troops. Wallace had little choice but to yield.

Source: History.com