Watson Warriner studied chemical engineering. But the tall, gregarious Virginian with the gift of gab wanted to be a salesman.

His initial foray into the field lasted only eight months. The prospect of a $10 raise brought him from Chicago to Wilmington, where he took a job with DuPont in February 1939.

Together, they would make history - a story of a technological achievement of remarkable yet horrific proportions that ended World War II. Warriner and DuPont were key players in the Manhattan Project - the secret development of the atomic bomb. The 1945 detonation of two of the devastating weapons ended World War II.

"DuPont's role was absolutely vital," said Erik Rau, a historian whose specialties include the history of industrialization and who also directs Wilmington's Hagley Library, a leading business history repository. "They turned to DuPont because of all of its chemical expertise, and its production facilities expertise.

"This was a project that couldn't fail."

Many who were involved in the top secret effort had no idea what they were working on, largely due to a policy of "compartmentalization" that limited the amount of information known to any one person. Warriner, who had a top secret Department of Energy "Q" clearance, was one of the few who did.

"I knew pretty well what we were doing ... We were going to make a bomb," said Warriner, now 96 and a resident of the ACTS Country House retirement home near Winterthur.

DuPont, already supplying nylon for parachutes and nearly half of the TNT U.S. forces would use, built the vast nuclear complex and supporting city in Hanford, Wash., where the plutonium was created for the second bomb dropped on Japan. Warriner oversaw construction of one of the long, thick concrete processors in which the man-made element was produced.

There, at a complex in Oak Ridge, Tenn., and at Los Alamos, N.M., work on the bombs and bomb material took place in absolute secrecy.

Warriner, a 1938 Virginia Tech graduate, had come to DuPont to produce neoprene, a synthetic rubber the chemical giant had introduced seven years earlier. The following year, he and four other engineers were transferred to Memphis to oversee construction of the Tennessee Powder Company, where smokeless powder would be produced.

"We built that plant and got it up and running in six months," Warriner said. "It was like a small Manhattan Project."

More chemical plant construction jobs for Warriner followed - in Alabama and Indiana - as DuPont's production of conventional explosives rose, particularly following the December 1941 Japanese attack on Pearl Harbor and America's entrance into World War II. DuPont had been an explosives producer since its 1802 launch.

Then, in February 1943, the manager at the Indiana plant called Warriner into his office and showed him a telegram from DuPont's chief engineer: "Watson is to report to Wilmington immediately." Warriner and his 1940 Ford convertible coupe were put on an eastbound train.

"So I reported to Wilmington, spent the night at the DuPont Hotel," Warriner said. At breakfast there, he ran into several other engineers, most of whom he knew, who had come in from different projects.

"I said, 'What are you guys doing here?' None of them knew, asking, in turn, "What are you doing here?" I said, "I don't know, either."

All were taken up to the Engineering Department. "They read us the Espionage Act," he said. They were asked if they understood what they'd been read; it didn't escape anyone that passing classified information to the enemy could be punishable by death. "It was very impressive," Warriner said. "So that was the way we were sworn in to the Manhattan Project."

The Manhattan Project oversaw the simultaneous development of two types of nuclear devices: one uranium-based and one that relied on plutonium implosion. Chicago-based nuclear scientists developed the technical aspects of the reactors and separation plants in Hanford and Oak Ridge. DuPont built the plutonium pilot plant at Oak Ridge and everything at Hanford, which encompassed an area one-third the size of Delaware.

Warriner spent the next year in Wilmington, first working on the design of plants that would produce "heavy" water - which contains a form of hydrogen used in nuclear reactors. Within six months, he was transferred to the separations section to help design plants where plutonium could be separated from uranium.

Then, in January 1944, he was told he'd be moving to Hanford, Wash., to put those plans into action. It would be the site of the world's first large-scale plutonium production.

Warriner was an expert in the process of nitric acid production, which was the critical component in the chemical process for large-scale plutonium production. Nitric acid dissolved the aluminum cans needed to hold the irradiated uranium slugs, and then was used to reduce the uranium down to the syrupy solution of plutonium nitrate that would be transported to the bomb-makers at Los Alamos.

It was, said Rau, a "gargantuan" undertaking. The 800-foot buildings - workers called them "canyons" - each required pump machines powerful enough to push the mix through 8-inch delivery lines a distance of 400 feet. Each building, Warriner said, contained 85,000 cubic yards of concrete - the same amount used to build the 47-story Mandarin Oriental Hotel in Las Vegas, completed in 2009.

The demand for secrecy produced some uncomfortable exchanges - particularly with older construction pros he found himself working with.

The pours, Warriner said, included the use of corrugated asbestos boards laid lengthwise between layers to reduce cracking. The concrete foreman took issue with that, saying the boards should be laid perpendicular to the long layers. Warriner told him they couldn't do that.

"So he looked at me rather curiously and said, 'You know, sonny, I was pouring concrete before you were born.' I said I know that, but it's still gotta go that way. I was diplomatic with him.

"So I had him come in with a senior construction man, my boss," Warriner said. "He sat down and said, 'Look, the reason Watson is here is to make sure that these buildings are built exactly like the drawings call for.' So I showed him the drawings again. And he said, `Well, I'll do that, but why does it have to do that?' His boss, he recalled, said, "I don't know why, 'cause he can't tell us. Just do it."

Warriner laughed that cackly laugh of his. The reason, he said, was so the lengthwise forms would better block radiation emanating from inside. But he was sworn to secrecy.

The plants went into production that fall, and the first plutonium produced was delivered to Los Alamos in February 1945.

Warriner was long gone. He was called back from a hard-earned vacation after one day and transferred in the summer of 1944 to DuPont, Wash., to oversee construction of nitric acid production equipment. The acid was destined for Hanford.

Once that plant was up and running in September, he was sent back to Alabama to the acid production facility where he'd worked in 1941. In early 1945, Warriner was sent to Picatinny Arsenal Works in Dover, N.J., another acid plant.

In June - about the time a group of Chicago-based scientists sent a petition to the White House arguing that atomic bombs be used against Japan only as a last resort, citing moral concerns - Warriner got married in Memphis. Ann Grymes was the lucky girl.

Warriner was far removed from Hanford on Aug. 6, 1945, when his new bride confronted him at their Budd Lake home after he came home from work.

"Watson, I know what you did in Hanford now," she said. Surprised, and still sworn to secrecy, he paused, then replied, "Ann, it's a beautiful day. How come you bring this up?" She said, "Come listen to this radio. They've dropped a bomb on a Japanese city and completely wiped it out." So I went in and listened to the news.

"What do you think about this?" Warriner recalled Ann asking. "And I said, 'Thank heavens, the thing worked!' " It was the uranium-fueled bomb, "Little Boy," that had been dropped on Hiroshima. Three days later, "Fat Man," powered by the plutonium that had been produced at Hanford, was dropped on Nagasaki.

"And that ended the war," Warriner said. Six days later, on Aug. 14, 1945, President Truman announced that Japan would surrender.

Warriner's reaction stemmed partly from an engineer's excitement at a project's successful outcome.

The Hiroshima bomb killed an estimated 70,000 people, while an estimated 39,000 initially died at Nagasaki. Cancer and birth defects afflicted many survivors and their children. The future would bring, as the scientists feared, the possibility of a world "in continuous danger of sudden annihilation."

But most Americans, hardened by the shock of the 1941 surprise attack on Pearl Harbor, the deaths of 405,399 U.S. troops and ready to end four years of war-related work, scrap metal drives and rationing, harbored few misgivings.

When he returned to work after Little Boy was detonated, a construction engineer he worked with at Picatinny came down to his office. The man said, "Well, they don't need no more dynamite or anything like that from DuPont, so you're probably going out of business." Warriner just shrugged him off.

"We had received notice from our management: do not reveal anything on the Manhattan Project until you have seen it in the newspaper," he said.

"So I just said, well, that's too bad - I'll be looking for a job. Well, three days later, our bomb went off. They still maintained that idea so I said, well, it's too bad. They had no idea that DuPont had done the whole damn thing!"

Warriner laughed again.

DuPont hadn't done it all, but the company had made an immense contribution to the war effort. Nylon for parachutes, mosquito netting and surgical sutures, powder bags, tires, Teflon and, of course, explosives. It was but the 15th-ranked U.S. corporation in terms of wartime contracts - partly because, sensitive to the "merchants of death" descriptor it had acquired popularly after World War I, it accepted only $1 for its work on the Manhattan Project.

After the war, Warriner began working at the Edgemoor plant where DuPont still produces titanium dioxide.

But Warriner still missed sales. In 1955, he convinced DuPont to let him make a lateral move, and he started marketing the company's plastics products. Warriner stayed with the company for another 26 years, retiring in 1981. Along the way, he'd earned a professional engineer's license. So, not skipping a beat, he took a job with EMC Process Company in Newport as a manufacturer's representative.

These days, Warriner lives alone - Ann died in 2005. A tall man, he carries himself well, although he employs a cane when standing. And he's still got the gift of gab.

He says he's outlived his contemporaries. Any record of DuPont employees who worked at Hanford either does not exist or could not be located. The only acknowledgment of Warriner's involvement in the project lies in an understated, framed certificate on the wall of his apartment.

"This is to certify that Watson C. Warriner has participated in work essential to the production of the Atomic Bomb," it states. "Awarded in appreciation of effective service." The paper is signed by Henry L. Stimson, secretary of war.

Warriner harbors no regrets about the devastation he helped bring about, and for two reasons: the blood the Axis powers shed while trying to dominate the world, and the blood thousands of U.S. troops most believed would have shed trying to invade the Japanese mainland.

For Warriner, it was all about putting an end to tyranny.

"I don't hate anybody in the world," he said. "I don't hate the Japanese, don't hate the Germans.

"But the morals of doing this was, we were fighting two vicious empires," he said. "Here the Germans - much as I admired the Germans - they put 6 million Jews to death. And the Japanese? They had invaded places like the Philippines and actually gone through hospitals, beheaded people, mothers in hospital beds. I actually saw a photo of this - with a baby pinned on the end of a bayonet stuck in a wall. Just terrible, horrible things.

"So it was morally correct to do what we did."