This is big.

On Thursday United States Defense Secretary Ashton B. Carter said he is officially opening all jobs in combat to women, a monumental announcement that was made after a groundbreaking three-year research period that looked at what military roles should be opened (or closed) to women.

What does it mean?

It means that about 222,000 jobs and 10 percent of the armed forces that were previously closed to females, are now open.

It means the Navy SEALs, Army Special Forces, Special Operations Units and the Marine Corps infantry are now all open to women.

The Marines had relented previously with the anticipation of the decision, even going as far as saying that their role of machine gunner — specifically — remain strictly a job for men. But, Carter said he is absolute with his decision, and the USMC’s request will not be fulfilled.

“There will be no exceptions,” Carter said. “This means that, 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.”

Watch him make the landmark announcement in the following clip:

This from the Washington Post:

The decision is nearly three years in the making. In January 2013, the defense secretary at the time, Leon Panetta, announced that he was rescinding a longtime ban on women serving directly in ground combat units, but gave the services until this fall to research the issue.

Each service chief provided recommendations in September, and Marine Gen. Joseph F. Dunford, chairman of the Joint Chiefs of Staff, reviewed them afterward. Carter told reporters at the Pentagon in September that he would be “very facts-based and analysis-based” once the decision reached him.

The issue has at times opened an uncommonly public rift between senior military leaders. In particular, Navy Secretary Ray Mabus took issue with a Marine Corps study that found that the average woman struggled to keep up with men, according to a number of metrics. The study did not track individual performance, drawing fire from Mabus and others in favor of full integration.