A soon-to-be-completed study on the U.S. Navy’s force structure could call for an increase in the service’s requirement for 48 Virginia-class fast-attack submarines, two Navy officials said July 14.

The Navy’s plan for 48 submarines was formulated over a decade ago, and much has changed in the world since then, including the increased possession of sophisticated arms by potential adversaries, said Rear Adm. Charles Richard, director of undersea warfare, and Rear Adm. Michael Jabaley, program executive officer for submarines.

Our competitors are pursuing advanced weapon systems at levels and at a pace of development not seen since the mid-1980s,” the admirals wrote in a joint statement to lawmakers. “We are returning to a time of major power competition between recognized states, not merely the insurgencies we have become accustomed to in the last 15 years.”

Russia, for instance, has become more assertive in its relations with the West, and the United States may need to respond accordingly, Richard said.

“In 2006, we had a very different relationship with Russia,” Richard told the House Armed Services Committee’s seapower and projection forces panel. “The relationship we have now may require additional forces.”

Adm. John Richardson, Chief of Naval Operations, said last month that he expects the study to be finished by August. The results could have major implications for General Dynamics [GD] Electric Boat and Huntington Ingalls Industries [HII] Newport News Shipbuilding, both of which build Virginia-class subs.

Even meeting the 48-submarine requirement could be a challenge due to decades of past budget decisions, the admirals acknowledged. The attack submarine fleet is expected to drop to 41 between 2025 and 2030, they testified. The Navy hopes that further development of unmanned systems and longer-range weapons will help alleviate that shortfall.