By WILLIAM J.BROAD


In 1945, after the atomic destruction of two Japanese cities, J.Robert Oppenheimer expressed foreboding about the spread of nuclear arms.

“They are not too hard to make,”he told his colleagues on the Manhattan Project at Los Alamos, New Mexico.“They will be universal if people wish to make them universal.”

That sensibility, born where the atomic bomb itself was born, grew into a theory of inevitability. Because the laws of physics are universal, the theory went, it was just a matter of time before other bright minds and determined states joined the club. A corollary was that trying to stop proliferation was quite difficult if not futile.

But nothing, it seems, could be further from the truth. In the six decades since Oppenheimer’s warning, the nuclear club has grown to only nine members. What accounts for the slow spread? Can anything be done to reduce it further? Is there a chance for an atomic future that is brighter than the one Oppenheimer foresaw?

Two new books by three atomic insiders hold out hope. The authors shatter myths, throw light on the dynamics of nuclear proliferation and suggest new ways to reduce the threat.

Neither book endorses Oppenheimer’s view that bombs are easy to make. Both document national paths to acquiring nuclear weapons that have been difficult and dependent on the willingness of spies and politicians to divulge state secrets.

Thomas C.Reed, a veteran of the Livermore weapons laboratory in California and a former secretary of the Air Force, and Danny B.Stillman, former director of intelligence at Los Alamos, have teamed up in “The Nuclear Express: A Political History of the Bomb and Its Proliferation” to show the importance of spies, scientists with divided loyalties and - most important - the subtle and not so subtle interests of nuclear states.

“Since the birth of the nuclear age,”they write,“no nation has developed a nuclear weapon on its own, although many claim otherwise.”

Among other things, the book details how secretive aid from France and China helped spawn five more nuclear states.

Secret cooperation extended to the secluded sites where nations tested their handiwork in thundering blasts. The book says, for instance, that China opened its sprawling desert test site to Pakistan, letting its client test a first bomb there on May 26, 1990.

In another disclosure, the book says China“secretly extended the hospitality of the Lop Nur nuclear test site to the French.”

All paths stem from the United States, directly or indirectly. One began with Russian spies that deeply penetrated the Manhattan Project. Stalin was so enamored of the intelligence haul, Mr.Reed and Mr.Stillman note, that his first atom bomb was an exact replica of the weapon the United States had dropped on Nagasaki.

Moscow shared its atomic thefts with Mao Zedong, China’s leader. The book says that Klaus Fuchs, a Soviet spy in the Manhattan Project who was eventually caught and, in 1959, released from jail, did likewise. Upon gaining his freedom, the authors say, Fuchs gave the mastermind of Mao’s weapons program a detailed tutorial on the Nagasaki bomb. A half-decade later, China surprised the world with its first blast.

Alarmingly, the authors say one of China’s bombs was created as an“export design”that nearly “anybody could build.”The blueprint for the simple plan has traveled from Pakistan to Libya and, the authors say, Iran. That path is widely assumed among intelligence officials, but Tehran has repeatedly denied the charge.

China’s aid to Pakistan also helped A.Q.Khan, a rogue Pakistani metallurgist who sold nuclear gear on the global black market.

A lesser pathway involves France. The book says it drew on Manhattan Project veterans and shared intimate details of its bomb program with Israel, with whom it had substantial commercial ties.

“The Bomb: A New History,”due out in January, looks more widely at proliferation curbs and diplomacy. It is by Stephen M.Younger, the former head of nuclear arms at Los Alamos and former director of the Defense Threat Reduction Agency at the Pentagon.

The two books draw on atomic history to suggest a mix of old and new ways to defuse the proliferation threat. Both see past restraints as fraying and the task as increasingly urgent.

Dr.Younger notes how political restraints and global treaties worked for decades to curb atomic proliferation, as did American assurances to its allies.

“It is a tribute to American diplomacy,”he writes,“that so many countries that might otherwise have gone nuclear were convinced to remain under the nuclear umbrella of the United States.”

And he emphasizes the importance of political incentives and punishments to halting and perhaps reversing the spread of nuclear arms. Iran, he says, is not fated to go nuclear.

“Sweden, Switzerland, Argentina and Brazil all flirted with nuclear programs, and all decided to abandon them,”he notes.

“Nuclear proliferation is not unidirectional - given the right conditions and incentives, it is possible for a nation to give up its nuclear aspirations.”