WASHINGTON — The Army National Guard will move most of its brigades under the command of its eight division headquarters as it reorganizes its fighting formations to give the force more combat power and some soldiers new career opportunities, officials said.

The Guard move will mark a substantial increase in the number of fully manned divisions that the Army can deploy, as only the service’s 10 active-duty divisions are now filled out with subordinate units, said Lt. Gen. Daniel Hokanson, the director of the Army National Guard. The increase to 18 complete Army divisions comes at a time when service officials believe a major conflict with a near-peer rival — namely Russia or China — would require the employment of full divisions, he said.

For the last two decades, the Army has focused on its smaller brigade combat teams as its primary fighting elements for counterterrorism operations and deployments focused on assisting the forces of other nations.