Why did president eisenhower send federal troops to integrate a little rock high school?

In September 1957 the school board in Little rock, Arkansas, won a court order to admit nine African American students to Central High a school with 2,000 white students. The governor ordered troops from Arkansas National Guard to prevent them from entering the school. The next day as the National Guard troops surrounded the school, an angry white mob joined the troops to protest the integration plan and to intimidate the AA students trying to register. The mob violence pushed Eisenhower's patience to the breaking point. He immediately ordered the US Army to send troops to Little Rock to protect and escort them for the full school year.