It is paradoxical that it is relatively rare to find armed personnel on a military base, other than the Military Police.
But soldiers, sailors and Marines who bristle with arms on the battlefield are scrupulous about keeping weapons and ammunition under lock and key on the home base.
And so it was that a man armed to the teeth (and a coward at heart) could murder13 men and women, including one civilian, at Fort Hood, Texas, with almost no chance that anyone would shoot back.
Maj. Nidal Malik Hasan has been charged with 13 counts of premeditated murder in the military's legal system, making him eligible for the death penalty if convicted.
As funerals for the victims go forward, and the president pays tribute to the courage and sacrifice of the dead and 38 others injured in the slaughter, attention also shifts to the accused.
The fact that Hasan is a Muslim, his capabilities as a psychiatrist and his allegiance to the Army and to the United States are all under scrutiny, both in the media and in the military.
Also, his outspoken resistance to his imminent deployment to Afghanistan, hiscommunications with a questionable imam overseas and provocative statements to others in the military and at his Falls Church, Va., mosque have drawn attention.
The overwhelming majority of Muslims in this country are peaceful and loyal to American ideals. Caution against prejudices -- including our own -- is warranted.
But is it possible that clear warning signals in Maj. Hasan's behavior and attitudes were ignored out of an overabundance of caution against profiling?
That's an important question.
President Obama has ordered a review of the intelligence system in place before the shootings in the Soldier Readiness Processing Center.
The Associated Press reports that in ordering the review, President Obama wants to know whether the information was properly shared and acted upon within government agencies.
John Brennan, assistant to the president for homeland security and counterterrorism, has been given charge of the inquiry.
Rep. Peter Hoekstra of Michigan, the top Republican on the House Intelligence Committee, and other members of Congress have called for a full examination of what government agencies knew about Hasan's contacts with the radical imam and other troubling activities, and what they did with the information.
Coverage of this terrible event brings out another related truth about our military members.
Their courage is not dependent upon sidearms.
Even as the semiautomatic pistols fired and fired and were reloaded and fired again, the troops in the center tried to fight back, flesh and bone against flying lead. Some fell to at once, giving CPR and other emergency aid to their fallen comrades, even though in some cases they were injured and still in danger themselves.
Ironically, it was civilian Fort Hood police officers who brought down the shooter, even as they came under fire themselves and one was wounded.
Accidental death at a military base is not terribly unusual, although it always is terrible.
The machines of war -- tanks, explosives, vehicles of all kinds, lethal weapons by the thousands -- are inherently dangerous and they are everywhere on military bases.
Each instance is a tragedy.
But deliberate mass murder rises from the level of tragedy.
It is the stuff of horror.