Colin Powell dies of complications from Covid.

Colin L. Powell, who in four decades of public life served as the nation’s top soldier, diplomat and national security adviser, and whose speech at the United Nations in 2003 helped pave the way for the United States to go to war in Iraq, died on Monday. He was 84.

He died of complications of Covid-19, his family said in a statement. He had been fully vaccinated and was treated at Walter Reed National Military Medical Center, in Bethesda, Md., where he died, his family said. Mr. Powell had undergone treatment for multiple myeloma, which compromised his immune system, a spokeswoman said.

Mr. Powell was a path breaker serving as the country’s first African American national security adviser, chairman of the Joint Chiefs of Staff and secretary of state.

Born in Harlem of Jamaican parents, Mr. Powell grew up in the South Bronx and graduated from City College of New York, joining the Army through the Reserve Officer Training Corps program. From a young second lieutenant commissioned in the dawn of a newly desegregated Army, Mr. Powell served two decorated combat tours in Vietnam. He was later national security adviser to President Ronald Reagan at the end of the Cold War, helping to negotiate arms treaties and an era of cooperation with the Soviet president, Mikhail S. Gorbachev.

As chairman of the Joint Chiefs, he was the architect of the invasion of Panama in 1989 and of the Persian Gulf war in 1991, which ousted Saddam Hussein from Kuwait but left him in power in Iraq. Along with then-Defense Secretary Dick Cheney, Mr. Powell reshaped the American Cold War military that stood ready at the Iron Curtain for half a century. In doing so he stamped the Powell Doctrine on military operations — armed with clear political objectives and public support, use decisive and overwhelming force to defeat enemy forces.

When briefing reporters at the Pentagon at the beginning of the gulf war, Mr. Powell succinctly summed up the military’s strategy to defeat Saddam Hussein’s army: “Our strategy in going after this army is very simple,” he said. “First, we’re going to cut it off, and then we’re going to kill it.”

It was a concept that seemed less suited to the messy conflicts in the Balkans that came later in the 1990s and in combating terrorism in a world transformed after the attacks on Sept. 11, 2001.