Complex sentence: They wanted to persuade the president to remove federal troops that he had sent there to maintain order, but Eisenhower kept troops in the city for the remainder of the 1957-1958 school year.
Split into simpler sentences: They wanted to persuade the president to remove federal troops he had sent there to maintain order. But, Eisenhower kept troops in the city for the remainder of the 1957-1958 school year.