American women demonstrated that they were fit to serve and could excel in combat long before the Pentagon set out in 2013 to do away with male-only career fields in the armed forces. After a painstaking review, Defense Secretary Ashton Carter announced last week that the military would open all ground combat jobs to women.

“There will be no exceptions,” Carter told reporters. “As long as they qualify and meet the standards, women will now be able to contribute to our mission in ways they could not before.”

It was a powerfully symbolic and sound policy move. While there will be logistical challenges as the Pentagon continues to break down barriers for women, doing so will make the military stronger and will narrow America’s gender equality gap.

There were, however, troubling signs that Carter could face political opposition and bureaucratic foot-dragging as the new policy is carried out.

The chairman of the Joint Chiefs of Staff, Gen. Joseph Dunford Jr., did not appear alongside Carter when he made the announcement. General Dunford, a Marine, has argued that a few jobs should remain closed to women. And Sen. John McCain, R-Ariz., the chairman of the Senate Armed Services Committee, issued a terse statement saying that lawmakers would “review the implications” of a decision that he said would have “a consequential impact on our service members and our military’s warfighting capabilities.”

Their attitudes echo those of leaders who decades ago warned about the perils of integrating African-Americans in the military and, more recently, suggested that allowing openly gay people to serve in uniform would hurt unit cohesion.

The naysayers this time appear to be driven primarily by sexism. The military, after all, has long been led by men. Its pre-eminent jobs have been reserved for men. And in recent decades, even as women have been allowed to serve more closely with men and in more types of jobs in the armed forces, many have felt unfairly relegated to second-tier status. The announcement last week will accelerate the dismantling of the last gender barriers.