Women will be allowed in all combat positions throughout the U.S. military, ending decades of exclusion from front-line jobs, Defense Secretary Ash Carter announced Thursday.

"To succeed in our mission of national defense, we cannot afford to cut ourselves off from half the country's talents and skills," Carter told reporters at the Pentagon.

The change, which will be implemented within 30 days, will open almost 220,000 reconnaissance, infantry, and special-operations positions that were not previously available to women. Women will have access to any position in the armed services whose requirements they can fulfill, Carter said.