David Kaiser is a war historian, sabermetrics enthusiast and a perennial thorn in the side of his alma mater, Harvard University.

Kaiser leads a group from the class of 1969 that has pushed Harvard to defend why it pays more than any other university for staff overseeing its $32.7 billion endowment. The group includes academics, an artist, a pastor and two lawyers -- all tracing their activism to anti-war protests that defined their college experience. Some members are gathering for the class’s 45th reunion, which begins today in Cambridge, Massachusetts.

“None of us were radicals back in college, but David has led us in giving voice to the spirit of the ’60s that Harvard needs to do a better job of serving its ideals,” said Kenneth Jost, a journalist who writes about the U.S. Supreme Court and teaches law at Georgetown University in Washington.

In the group’s latest move, Kaiser and eight other members wrote to Harvard President Drew Faust demanding to know why compensation at the endowment doubled in three years. The letter came as the university searches for a replacement for Jane Mendillo, who oversees the endowment.

The group coalesced more than a decade ago sparked by outrage as individual pay for some top traders at Harvard Management Co., the Boston-based firm that manages the world’s largest university endowment, reached $35 million a year. The group evolved into a watchdog, and again attacked the school in 2009 for paying bonuses to endowment staff during the global credit crisis when investments fell an unprecedented 27 percent.