Refer to the passage below to help you answer the question. After the Brown V Board of Education decision, the NAACP attempted to register black students in previously all-white schools in cities throughout the south. In Little Rock, Arkansas the school board agreed to comply with the court’s ruling with a plan of gradual integration to begin in September 1957.
The NAACP registered 9 black students to attend the previously all-white Little Rock Central High, selected on the criteria of excellent grades and attendance. Called the “Little Rock Nine”, they were: Ernest Green, Elizabeth Eckford, Jefferson Thomas, Terrence Roberts, Carlotta Walls LaNeir, Minnijean Brown, Gloria Ray Karlmark, Thelma Mothershed, and Melba Pattilo Beals.
When integration was scheduled to begin on September 4, 1957, the Arkansas National Guard was called in to “preserve the peace.” At the orders of the governor, the guard, along with a large white mob, blocked the entrance to the school and wild not allow the Little Rock Nine to enter. For the next 18 days President Dwight D. Eisenhower negotiated with the Arkansas governor and the Little Rock mayor. Eventually, president Dwight D. Eisenhower nationalized the guard and ordered them to support integration and protect the students. With the protection of the soldiers, the nine teenagers were able to attend school at Little Rock Central High. Although the students were continually harassed, the eight of the nine completed the academic year.

Question: what two roles did the Arkansas national guard play and why?