The latest American intelligence assessments on Pakistan’s nuclear arsenal have concluded that the South Asian nation has steadily expanded its nuclear might in recent years, with a total number of deployed weapons now ranging from the mid-90s to more than 110. When President Obama took office, his aides were told that the arsenal “was in the mid-to-high 70s,” according to one official. This new estimate puts Pakistan on track to overtake Britain as the world’s fifth largest nuclear weapons power, highlighting Pakistan’s determination to grow its arsenal, mostly to deter its regional rival, India. The growing numbers also challenge an integral element of Obama’s national security strategy: to reduce nuclear stockpiles around the world. Another worry is Pakistan’s production of nuclear materials. Based on the latest estimates of the International Panel on Fissile Materials, an outside group that estimates worldwide nuclear production, Pakistan has now produced enough material for 40 to 100 additional weapons, including a new class of plutonium bombs.