AMHERST, Mass. – It has been many years since soldiers hunkered down in an underground war room near here, poised to unleash nuclear Armageddon with B-52 bombers.

Now a group of colleges hope to help convert swords into plowshares by taking the old Strategic Air Command bunker and making it store something much more creative: books.

The three-story, climate controlled, atomic-bombproof bunker was dug into a mountain above Westover Air Reserve Base in 1957 when it was the air command’s eastern headquarters.

Its purpose, as the backup for SAC headquarters in Nebraska, was to allow 300 men to hold out long enough to direct retaliatory strikes in case of nuclear war. They had air, food and water for 30 days.

It is now owned by Amherst College, and the small liberal arts college and four nearby schools – Mount Holyoke, Smith and Hampshire colleges and the University of Massachusetts – are converting it into a massive underground library.

“It’s so ironic. Here is something dedicated to war and we are storing library material in it,” said Amherst College librarian Willis Bridegam. “But there, it was 4.5 miles south of the campus. And why not?”

Amherst College bought the bunker for about $500,000 in 1992 from the Federal Reserve Bank of Boston, which acquired it after SAC pulled out of Westover in the 1970s.

The college has spent another $1 million on renovations, primarily to convert the old walls of carbon filters and fans into a modern climate and humidity control system to keep the bunker at a steady 70 degrees and 46 percent humidity.

“It would be three to four times more expensive to house these books on campus,” Bridegam said. Before the bunker went on the market, college trustees had balked at building a new $30 million building to ease the library’s space squeeze.

“It’s wonderful,” said Harry Wolfe, a former Air Force officer who served in the bunker during the Cuban missile crisis in October 1962 and is one of the town’s library trustees. “I hated to see it go to waste. And we need to preserve books.”

Other surplus bunkers have been turned into museums or storage for business records. The Greenbrier Resort in West Virginia offers tours of its bunker, meant to house Congress in case of nuclear attack, and has toyed with converting it into a gambling casino.

Amherst’s bunker will hold about 500,000 of the colleges’ lesser-used books and journals. The 9.5 miles of underground shelves will be filled over the next decade with volumes packed according to size, not subject, and marked by bar codes retrievable by computers, Bridegam said.

Most items will never leave the bunker, said David Spoolstra, who oversees the five-college section of the depository, housed in the area that once held room-sized battle computers.

It’s what research librarians call a “light archive,” meaning the works will be available only on request. Only archive workers will have access to the stacks and in most cases will provide academic researchers with an electronic copy, Bridegam said.

Few traces remain inside of the bunker’s military history, except for the glassed-in balcony overlooking the war room. The sign on the door still reads “Senior Battle Staff Only,” but the two-story war room is now filled with books awaiting shelving.

The 3-foot thick, lead-lined blast doors are gone, sold for scrap.

“We tried to find a buyer, but there were no takers,” said Aaron Hayden, capital projects manager for the college.

The mustard yellow and green paint on the concrete walls has been replaced with bright whitewash.

The 3-foot-high false floors that had hidden miles of cabling for the old computers have vanished – along with the Cold War-era girlie magazines that library workers discovered tucked away in the crawl space by long-ago airmen.

But the roof – 4 feet of lead-reinforced concrete topped by another 10 feet of stone – is still solid. And the 18-inch-thick concrete floors are a librarian’s delight.

“They will hold 500 pounds of books per square foot,” said Hayden.