Peter Rodman, a foreign policy expert who served every Republican president from Richard Nixon to George W. Bush, including as an assistant secretary of defense for nearly six years in the current administration, died Saturday in Baltimore. He was 64.
The cause was complications of leukemia, said Danielle Pletka, vice president of foreign and defense policy studies at the American Enterprise Institute.

Rodman was lured into government by his senior thesis adviser at Harvard, Henry Kissinger, then the national security adviser, and he became Kissinger’s aide in negotiations that included opening ties to China, peace talks on Vietnam and the Arab-Israeli conflict.

As assistant secretary of defense for international security affairs, he traveled with Defense Secretary Donald Rumsfeld to gather allies for the war on terrorism in Afghanistan, Iraq and elsewhere.

He led a mission to London to help establish the multinational peacekeeping force for Kabul after the overthrow of the Taliban.

His jobs included being director of the State Department’s policy planning staff; a senior editor at National Review; and director of national security programs at the Nixon Center, a foreign policy research organization. He had been a senior fellow in foreign policy at the Brookings Institution since March 2007.

Peter Warren Rodman was born on Nov. 24, 1943, in Boston. He became interested in foreign policy at 4 and later taught himself Russian to listen to Soviet broadcasts, his family said. He graduated summa cum laude from Harvard in three years and earned a master’s degree from Oxford and a law degree from Harvard.

In 1994, he published “More Precious Than Peace: The Cold War and the Struggle for the Third World,” a study of Soviet-American competition in the developing nations that Foreign Affairs called a “tour de force.” Next year, Knopf is to publish his “Presidential Command: Power, Leadership, and the Making of Foreign Policy from Richard Nixon to George W. Bush,” which melds his own experiences with extensive research.

Rodman also worked extensively with Kissinger on the former secretary of state’s memoirs and published many monographs and articles, some in the popular press.