April 3, 2014 5:58 AM EDT

In the summer of 1974, as the Watergate crisis reached its apogee, Secretary of Defense James Schlesinger, fearing that President Richard Nixon had become unstable, ordered the military to disregard White House orders unless they were cleared by him or Secretary of State Henry Kissinger. When Nixon resigned, Schlesinger drew up plans to deploy troops to Washington in case of problems with the presidential succession. After that long national nightmare, Schlesinger remained Defense Secretary and, according to historian Walter Isaacson, “set himself up as Kissinger’s intellectual rival in the Ford Administration.”

Schlesinger served as a Cabinet officer under three Presidents through often stormy times. An economist who specialized in national security, he was chairman of the Atomic Energy Commission before rising to become Nixon’s Secretary of Defense. During a 17-week tenure as head of the CIA in 1973, he forced out nearly 10% of the agency’s staff after learning of CIA spying on Americans. While he was at the Pentagon, the U.S. modernized its weapons systems and kept pace militarily with a rising Soviet Union. And under Jimmy Carter, Schlesinger was the first Secretary of Energy, a job in which he strongly supported nuclear power. When asked in 2013 to grade government management of energy over the past 40 years, Schlesinger gave the U.S. “a high D+.” “We’re sometimes on the verge of achieving a C,” he said, “but never quite get there.”

–NATE RAWLINGS

This appears in the April 14, 2014 issue of TIME.

Contact us at letters@time.com.

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