BOSTON -- Boston University professor Andrew Bacevich has repeatedly railed against the Iraq war in op-ed columns and interviews.

But now he's mourning the loss of his son, who he learned this week was killed in Iraq.

The military said Army 1st Lt. Andrew J. Bacevich, 27, of Walpole, Mass., died May 13 in Balad, Iraq, when an improvised explosive device detonated near his unit in Salah Ad Din province."

He was assigned to the 3rd Battalion, 8th Cavalry Regiment, 3rd Brigade Combat Team, 1st Cavalry Division, at Fort Hood, Texas, the military said.

After graduating from West Point and Boston University, he worked in politics beginning in 2003, first as an intern for the late Republican Sen. Strom Thurmond of South Carolina, and later as a legislative aide to then-Gov. Mitt Romney.

Romney said Tuesday that he talked with Bacevich about his decision to enlist before he left the Massachusetts Statehouse.

"I got to know Andrew as a legislative aide in my office, and before he left we met and talked about his plans," Romney said in a statement. "He was driven by a desire to serve, first as part of our team and then as a member of the military. His loss is a deep personal loss for me and for all of those who knew him."

His father is professor of international relations at Boston University, where he served as the Director of the Center for International Relations for five years. A conservative, he viewed the war as an overreach by political and military leaders who overestimated the power of the American military to transform the Middle East.

The university's Web site said the elder Bacevich is the author of "The New American Militarism: How Americans Are Seduced by War," "American Empire: The Realities and Consequences of U. S. Diplomacy," and "The Imperial Tense: Problems and Prospects of American Empire."

"There are no easy answers, but one at least ought to acknowledge that in launching a war advertised as a high-minded expression of U.S. idealism, we have waded into a swamp of moral ambiguity," he wrote in the Washington Post in July 2006.

Bacevich advocated withdrawal from Iraq, writing in The Boston Globe in March that the war had made the world more dangerous for the United States.

Friends say Bacevich rarely mentioned his son was serving in the war, which the professor has described as a "catastrophic failure," in part to avoid any question that he was proud of his son's service.

Colleagues said the elder Bacevich, also a West Point graduate, retired lieutenant colonel and Vietnam veteran, would never have tried to discourage his son from joining the Army.

In a statement, Bacevich's family remembered him as a man of humor and handsome looks who had overcome the challenges childhood asthma to be an Army officer and a marathon runner.

"Andy was a born-leader who felt called to serve his country," the statement said. "Our family will miss him dearly and forever."