Conrad K. Harper had an urgent letter to deliver last month, so naturally, he turned to FedEx. “Priority Overnight,” he recalls. “Gets it there on time.”

The letter, Harper’s adieu to the Harvard Corporation, awoke the University from summer’s lull and added an intriguing postscript to the drama of last semester. “I guess you can say it arrived,” he said in an interview this week.

Indeed, the letter arrived—on time—at Massachusetts Hall the following morning, setting off a flurry of commotion among Harper’s suddenly former colleagues on the board. In the two weeks before the resignation would be officially announced, James R. Houghton ’56 and Robert E. Rubin ’60 tried repeatedly to change Harper’s mind, an individual familiar with the board’s discussions said. But their attempts were to no avail.

Harper’s resignation took much of the Harvard community by surprise, but his friends and colleagues said the decision fit squarely with their impressions of the man—whom nearly all of them call “principled.”

“He just is one of those people who always would answer the call whenever the moment called for it,” says Climenko Professor of Law Charles J. Ogletree, who has known Harper for more than 30 years. “Whenever it takes sacrifice and commitment, Conrad is there.”

Ogletree had prepared a statement—along with Henry Louis Gates Jr., chair of the African and African American studies department—calling on University President Lawrence H. Summers to release Harper’s letter before the president did so himself on Monday.

Harper refused last week to release the letter himself, saying it was up to Summers and the Corporation. He would comment on his reasons for not releasing the letter himself beyond saying that it was up to Harvard to release it.

Harper and Summers first crossed paths not in Cambridge but in Washington, D.C., where they were both serving in rival departments in the Clinton administration. Harper was top legal adviser to the State Department from 1993 to 1996 while Summers was working his way up the Treasury department.

Several of Harper’s friends say he was less than satisfied with Summers’ position on affirmative action in higher education, although they declined to elaborate Harper’s concerns. The friends spoke on the condition of anonymity because Harper treasures his privacy, they say. Harper himself declined to comment on the matter.

A New York lawyer who has worked with Harper on several occasions suggested that he had been strongly influenced by one of his mentors, Cyrus R. Vance, who resigned as Secretary of State in 1980 after President Carter ordered a hostage rescue mission in Iran over Vance’s objections.

“That incident must have had a profound effect on Conrad when he was still at the beginning of his legal career,” the lawyer said.

Harper’s resignation from the Corporation isn’t the first time he publicly protested his voice not being heard. As president of the New York City Bar Association in 1991, Harper published a piece in The Washington Post criticizing the first Bush administration for excluding his group from evaluations of judicial nominees.

“It is time for the Justice Department to live up to its name by renouncing the tactics of the bully and the methods of the tyrant,” Harper wrote. In an interview this week, he recalled that time as challenging. “We were very much at loggerheads with the Justice Department,” he said.

Harper, 64, argued his first case before the U.S. Supreme Court just four years out of Harvard Law School as an attorney for the NAACP Legal Defense Fund in 1969. The case, Daniel v. Paul, pitted African-American residents of Little Rock, Ark., against an all-white club that had denied them membership.

Harper won the case for the Little Rock residents. He also successfully negotiated the desegregation of the Chicago public schools in 1977, solidifying his status as a preeminent civil rights lawyer.