Harold Agnew, a leading figure of the nuclear age who helped design the first atomic bomb as a member of the Manhattan Project, has died. He was 92.

Agnew died Sunday while watching football at his home in Solana Beach, Calif., his family said in a statement released by Los Alamos. He had chronic lymphocytic leukemia.

In a career that spanned more than 50 years, Agnew held a unique vantage point on the nuclear era. A physicist who trained under Enrico Fermi, he helped build the world’s first reactor; flew alongside the Enola Gay when it dropped its devastating load on Hiroshima; and headed Los Alamos’ weaponry division during a prolific postwar period when the lab developed many new weapons. One of those was the thermonuclear warhead for the Minuteman intercontinental ballistic missile.

“Harold was an innovator,” said Los Alamos National Laboratory historian Alan Carr. “The vast majority of weapons in the nuclear stockpile were designed at Los Alamos and Harold had a hand in designing most of them.”

Agnew, in an interview with the BBC in 2005, said he considered his seminal contribution to building the U.S. nuclear arsenal to be “my legacy.” He remained an unapologetic hawk throughout his life, even after many of the leading scientists of the early nuclear era, including Albert Einstein and J. Robert Oppenheimer, expressed moral qualms about the bomb and its consequences.

“My feeling towards Hiroshima and the Japanese was, they bloody well deserved it,” he told the Los Angeles Times in 1984. “The whole damn thing has been turned around as if we were the bad guys.”

The blunt-spoken scientist had no qualms about advancing his views in Washington. He advised President Jimmy Carter against a comprehensive ban on nuclear testing in 1978, arguing that it would not only halt the development of new weapons but weaken the deterrence value of the existing arsenal. The White House ultimately abandoned the idea of a test ban.

At the same time, Agnew spearheaded efforts to substantially improve nuclear security. In the early 1960s, during an inspection of nuclear caches in Europe, he discovered that the only security on an armed U.S. plane was a lone American soldier with a rifle and no training on how to respond to a threat. Under Agnew’s tutelage, scientists at Los Alamos devised a coded safety system, called the permissive action link, to prevent arming a nuclear weapon without proper authorization.

Agnew oversaw the installation of the safety system on all nuclear weapons in Europe as scientific adviser to the Supreme Allied Commander in Europe from 1961 to 1964.

After the Cold War ended, he was instrumental in molding a new mission for Los Alamos, overseeing the creation of programs unrelated to defense, including projects involving nuclear energy, basic science and biomedical research.Agnew He earned a degree in chemistry from the University of Denver in 1942 and joined a research group headed by Fermi, the Italian-born physicist whose work led to the first controlled nuclear chain reaction. He followed Fermi to the Manhattan Project, the top-secret government program at Los Alamos, N.M., whose sole objective was to develop the atomic bomb.