Much of the planned modernization is nearly locked in because of the need for new weapons and because some of it is so far along, said Evan Montgomery, a senior fellow at the Center for Strategic and Budgetary Assessments, a Washington-based research group.
The B-21 long-range strike bomber and the replacement for the Navy's 14 Ohio-class ballistic missile submarines are "the two most expensive items, and they're arguably the two safest in a lot of ways," Montgomery said. The bomber can deliver both conventional and nuclear weapons, and the submarine is considered a priority because it would survive any first strike by an adversary.