The US Army said Friday it will commission 22 women as infantry and armor officers under historic new rules allowing females to serve in ground combat roles.

Defense Secretary Ash Carter in December announced a sweeping directive to open all military occupations to women this year, including front-line combat roles.

The 22 women have almost finished their officer training, but must still "conduct branch-specific initial training for several months at Fort Benning, Georgia," the Army said in a statement.

They must also demonstrate certain physical requirements before they are fully qualified to start.

Armor officers are responsible for tank and cavalry operations. Infantry officers lead infantry troops and other armed forces during land combat.

Although women warriors have frequently found themselves in combat situations in Iraq and Afghanistan, they had previously been barred from joining front-line combat roles, including the infantry and Special Forces.

Currently, women account only for about 15.6 percent of the 1.34 million active-duty personnel in the Army, Marine Corps, Navy and Air Force.

As the new rules kick in, 52 military occupations -- some 220,000 jobs -- will accept female applicants, who must still pass the same rigorous physical tests as men.