Washington — Defense Secretary Ash Carter has given his top commanders the green light to allow more troops to carry weapons at U.S. bases, with a focus on recruiting stations, Reserve centers and other softer military targets.

Carter’s actions came two weeks after a Kuwaiti-born gunman fatally shot four Marines and a sailor before police killed him at the Navy reserve center in Chattanooga, Tenn.

“The tragic shooting on July 16 in Chattanooga, Tennessee, illustrates the continuing threat to DOD personnel in the U.S. homeland posed by homegrown violent extremists,” Carter wrote in a memo released Thursday by the Pentagon.

In the memo, Carter gave his service chiefs and regional command heads until Aug. 21 to submit “action plans” for beefed-up security of personnel, buildings and other physical facilities.

“I am directing all components to consider any additional protection measures including changes to policy and procedures that protect our force against the evolving threat,” Carter wrote in the memo.

Armed citizen vigilante groups in a half dozen states started standing guard outside recruiting centers and other public military sites after the July 17 shooting rampage in Chattanooga.

In that assault, the shooter, later identified as Muhammad Youssef Abdulazeez, fired shots from his car at an armed forces recruiting center, and then drove six miles with police in pursuit, crashed through the Navy Reserve center’s security gate, left the car and ran through a building, firing as he moved.

The government has not classified the rampage as a terrorist attack but says Abdulazeez, 24, may have been a “lone wolf” assailant inspired by the Islamic State or other militant groups. Born in Kuwait before moving with his family to Tennessee, he’d made several visits to Jordan in recent years, ostensibly to see relatives.

The shooting was the deadliest criminal attack at a domestic military base since an Army psychiatrist shot and killed 13 soldiers and wounded 29 others in November 2009 at Fort Hood, Texas.

The psychiatrist, Nidal Malik Hasan, was later sentenced to death and is awaiting execution pending appeals at the Fort Leavenworth, Kan., military prison. At his August 2013 court-martial, Hasan, an American-born Muslim, said the shootings were an act of jihad against the United States.

In the days following the Chattanooga shooting, lawmakers from both parties pushed bills that would arm domestic service members.

But former senior military officers who are sharpshooters and have served in high government posts urged caution, saying many U.S. troops have only basic skills with weapons, especially those with no experience in combat or war zones.

The Pentagon came out against the idea of giving every domestic member of the military a gun.

“(There are) safety concerns, the prohibitive cost for use-of-force and weapons training, qualification costs as well as compliance with multiple weapons-training laws,” Navy Cpt. Jeff Davis, a Pentagon spokesman, told reporters.

In his memo this week, however, Carter noted that existing Pentagon policy gives commanders at U.S. installations “the option of (employing) additional armed personnel.”

Carter said that Defense Directive 5210.6, issued April 1, 2011, under then-Secretary Robert Gates, “allows for the arming of qualified DOD personnel (not regularly engaged in law enforcement duties) based on the threat and the immediate need to protect DOD assets and lives.”

That directive says military personnel “shall be appropriately armed and have the inherent right to self-defense.”

At the same time, however, the directive says: “Arming DoD personnel with firearms shall be limited and controlled.”

Attempting to balance competing needs of self-defense and safety, the policy adds: “Evaluation of the necessity to arm DOD personnel shall be made with the consideration of the possible consequences of accidental or indiscriminate use of those arms. However, the overriding factors in determining whether or not to arm are the mission and threat.”

In the aftermath of the Chattanooga shootings, Carter ordered Marines to stop wearing their uniforms at recruiting centers, which are especially soft military targets because many are located in shopping centers and other places easily accessible to civilians.

Some governors authorized their National Guard units to be armed, moved them to fortified armories or took other steps to increase security.