The team, believed to consist of four to six militants, destroyed two U.S.-supplied maritime surveillance aircraft and engaged security forces in hours of pitched firefights. It was not until late Monday afternoon that Pakistani forces regained full control of the facility…

The breach is likely to raise worries among leaders in the United States and Europe about the security of Pakistan’s approximately 100 nuclear weapons.

“I’m sure there will be concerns around the world about this, there’s no doubt about it,” said security analyst Talat Masood, a retired Pakistani general. “I think Pakistan will have to make certain that anything like this cannot be repeated from the standpoint of nuclear installations.”…

For militants to infiltrate sites storing the nuclear arsenal would require a level of sophistication not yet seen by the groups, Galbraith said. “It is one thing to be able to get 18 people into a secure base and kill 12 security guards. It is another thing to try to grab a nuclear weapon and take it out. And then what would they do it? Some of these concerns are overwrought.”