A jet fighter drops a mock B61 model 12 bomb that zeroes in on the target zone, as part of a $10 billion United States government program that seeks to build a smart atom bomb of great precision.
The United States military is replacing the fixed tail section of the B61 bomb with steerable fins and adding other advanced technology. The result is a bomb that can make more accurate nuclear strikes and a warhead whose destructive power can be adjusted to minimize collateral damage and radioactive fallout.
As Mr. Obama enters his final year in office, the debate has deep implications for military strategy, federal spending and his legacy.
The B61 Model 12, the bomb flight-tested last year in Nevada, is the first of five new warhead types planned as part of an atomic revitalization estimated to cost up to $1 trillion over three decades. As a family, the weapons and their delivery systems move toward the small, the stealthy and the precise.
Already there are hints of a new arms race. Russia called the B61 tests “irresponsible” and “openly provocative.” China is said to be especially worried about plans for a nuclear-tipped cruise missile. And North Korea last week defended its pursuit of a hydrogen bomb by describing the “ever-growing nuclear threat” from the United States.