In 2005, Mr. Lugar took a young senator, Barack Obama of Illinois, on his first trip as a new member of the Foreign Relations Committee to Russia, Ukraine and Azerbaijan, to examine dismantled weapons and sites. Mr. Obama later credited that trip with fueling a commitment to further reduce the size of the American arsenal after he was elected president three years later.

But while Mr. Lugar sometimes compared his efforts to those of George Marshall, the creator of the Marshall Plan that rebuilt Europe, he watched the fruits of his efforts begin to wilt in his last years. Under President Vladimir V. Putin, the Russians began to resent the American funding of the disarmament effort, and some Russians saw in it a Washington plot to further weaken their country. Mr. Putin set the country on the course of nuclear modernization, and Mr. Lugar, over a dinner several years ago, lamented that Mr. Obama had not been more aggressive in dismantling parts of the American arsenal that Mr. Lugar considered no longer necessary.

Roots in the Indiana Soil

Richard Green Lugar was born in Indianapolis on April 4, 1932, to a farming family with generations of roots in Indiana.

His early life and career were marked by the most traditional signposts of American success. He was an Eagle Scout and president of his Denison University senior class. He got along so well with his class’s co-president, Charlene Smeltzer, who was known as Char, that they married. She survives him.

He became a Rhodes scholar after graduating, and during his studies at Oxford, he visited the American embassy in London in 1956 to enlist in the Navy.

After his return to the United States, Mr. Lugar was commissioned an ensign and became a briefer for Admiral Arleigh Burke, the chief of naval operations, who had been a hero of World War II and was renowned as a guileful player in Washington politics. Friends said that this was Mr. Lugar’s most significant exposure to geopolitical thinking, and probably the single greatest source of his fascination with foreign policy.

After a few years back in Indiana running a machine business, Mr. Lugar was elected to the Indianapolis school board. His old high school was by then 90 percent African-American, and he pushed through a plan to make it one of the nation’s first integrated magnet schools for the college-bound. Shortridge High soon became evenly divided between black and white students.