Charles W. Sweeney, 84, who died of a heart ailment July 16 at a Boston hospital, was an Army Air Forces pilot during World War II whose first combat mission over an enemy target was the atomic bomb drop over Nagasaki, Japan.

On Aug. 6, 1945, three days before the Nagasaki attack, Mr. Sweeney piloted a weather-instrument plane flying in support of the Enola Gay, which bombed Hiroshima, Japan.

Mr. Sweeney unambiguously supported the bombings, which along with the Soviet invasion of Manchuria persuaded a recalcitrant Japanese government to surrender that month. The atomic attacks killed and mutilated tens of thousands of Japanese and helped deter an Allied incursion of mainland Japan that many historians believe would have cost untold numbers of lives.

Mr. Sweeney decried "cuckoo professors" and the "cockamamie theories" of those who believed the atomic bombing of Japan was unnecessary.

"I saw these beautiful young men who were being slaughtered by an evil, evil military force," he told a reporter in 1995. "There's no question in my mind that President Truman made the right decision" to release the bomb.

However, Mr. Sweeney did not try to aggrandize his role in the war.

"As the man who commanded the last atomic mission, I pray that I retain that singular distinction," he wrote in his memoir, "War's End" (1997).

Charles William Sweeney, the son of a plumber, was a native of Lowell, Mass. Entranced by the military planes that landed at a nearby airfield, he joined the Army Air Corps as an aviation cadet April 28, 1941.

He spent much of the war as an instructor and test pilot. In 1944, he was assigned to Wendover Field, in the Utah salt flats, where he worked under the command of Col. Paul Tibbets, who trained others for the atomic bombing mission and himself helmed the Enola Gay.

After the Enola Gay flight, the Japanese did not lay down arms. The order came for Mr. Sweeney to make his run over Japan in a B-29 Superfortress named the Bockscar. He was to drop another atomic bomb over Kokura, Japan; Nagasaki was an alternative target.

In flight, Mr. Sweeney encountered a mechanical malfunction that affected fuel release to the engines. The gas situation worsened as the Bockscar circled at a rendezvous point while waiting for a plane that failed to show. Hours later, over Kokura, the bombardier had trouble finding a target over the fogged-in city.

As antiaircraft fire cracked around the plane, a decision was made to head toward Nagasaki. The bomb whistled down, exploding nearly 2,000 feet over the city and sending a mushroom cloud funneling skyward.

"I could see a brownish horizontal cloud enveloping the city below," Mr. Sweeney wrote in his memoir. "From the center of the brownish bile sprung a vertical column, boiling and bubbling up in those rainbow hues -- purples, oranges, reds -- colors whose brilliance I had seen only once before and would never see again."

His decorations included the Silver Star and the Air Medal.

After the war, he rose to the rank of major general in the Massachusetts Air National Guard. In the early 1960s, he coordinated civil defense work in Boston, creating response plans in case of a nuclear attack on the United States.

He spent much of his career as a co-owner and operator of a leather brokerage business in Boston, often working with shoe manufacturers. He was former president of the Boston Boot and Shoe Club, a trade organization.

His marriage to Dorothy W. Sweeney ended in divorce.

Survivors include 10 children, two brothers, a sister and 24 grandchildren.

Charles W. Sweeney believed in the atomic bomb's necessity but said he hoped it would never be used again.