WASHINGTON — Americans began mourning over the weekend the loss of one of the country’s premier foreign policy thinkers and strategists, Peter Rodman. At 64, Rodman succumbed to leukemia, leaving behind his wife Veronique, his daughter Theodora, and his son Nicholas.

Rodman’s career in public service began as an assistant to Henry Kissinger during the Nixon administration, where he played a key role in opening the talks that led to the normalization of ties between Nixon’s America and Mao’s China. A former speechwriter for Mr. Kissinger, Mark Palmer, said that Rodman was “Henry Kissinger’s closest colleague, almost a son.” Mr. Palmer said that Rodman was “the only one he absolutely trusted. I was with them together a great deal from 1973-76, on trips across the globe and in Washington. Peter was the only one consistently invited to Henry’s most sensitive one-on-ones.”

In this capacity as one of Mr. Kissinger’s closest confidantes, he helped the former secretary of state write his memoirs, which to this day are primers in foreign policy for diplomats and journalists who cover the State Department. Rodman also wrote one of the most stirring defenses of the Reagan doctrine as it applied to countering communism in the third world, a book published in 1994, “More Precious Than Peace: Fighting and Winning the Cold War in the Third World.”

In this sense Rodman migrated in some ways in the 1980s and 1990s away from the realpolitik of Mr. Kissinger and more to the neoconservative approach exemplified by President Bush’s freedom agenda. He was a senior editor of National Review in the 1990s and also an original endorser of the Project for the New American Century, a policy group that advocated for, among other things, the overthrow of Saddam Hussein. In 1999 he wrote an essay for Freedom House, “Multilateralism and Its Discontents,” making the case that an America restrained by the United Nations may hamper the country from advancing the cause of human freedom, particularly in the case of Iraq.

Born in Boston, a graduate of Harvard College, Oxford University, and Harvard Law School, Rodman received praise for his breadth of knowledge and intellectual humility.

Mr. Rodman served in the Pentagon under Secretary of Defense Rumsfeld as assistant secretary of defense for international security affairs. Mr. Rumsfeld said: “Peter had a rigorous intellect, an unfailing sense of humor, and an understated manner. Over many decades, he worked energetically to find bipartisan support for our nation’s foreign policy at home and a consensus among diplomats abroad. Peter was a dedicated public servant, an incisive strategist, a consummate diplomat, a serious pupil of history, and a measured teacher of history’s lessons. I profited from his friendship. And I profited from his advice and his admonitions. So too did America.”

Douglas Feith, who worked with Rodman in the Rumsfeld Pentagon as undersecretary of defense for policy, said of Rodman: “He was highly intelligent, very well-read, very thoughtful, very measured in his judgments, and everybody commented on his gentlemanliness; he was just an elegant individual.”

Mr. Feith recalled that Rodman was a skilled diplomat in the early days of the global war on terror. Rodman was dispatched to London to negotiate the expansion of the international force protecting Kabul, Afghanistan, shortly after the fall of the Taliban. At the time, the British were in charge of what was known as the International Security Assistance Force, but the American army was planning operations throughout Afghanistan and had to make sure their operations would be harmonious with those of the British.

“Rumsfeld was very concerned ISAF not get crosswise with Centcom [Central Command]. We were joking we could set back U.S.-British relations to 1812, but Peter handled it,” Mr. Feith said. Mr. Feith added that the agreement Rodman negotiated became the model for the NATO force that remains in Afghanistan to this day.