Maj. Nidal Malik Hasan is accused of murdering last week 13 people (12 of whom were soldiers) and wounding another 30 at Fort Hood, Texas. It was not the first, nor will it be the last, domestic terrorist incident since Sept. 11, 2001.

We now see that authorities had, or should have had, reason to be suspicious of Hasan — including his contact with a radical cleric and a bizarre "medical" presentation he once gave to Army doctors that focused on Islam and the military.

We're also learning that someone going by the name Nidal Hasan posted extremist views on the Internet, and at least one former classmate questioned his loyalty to America.

Yet no one acted.

Was, as there appears to be, a fear among would-be accusers of being charged with politically incorrect bias?

That worry has certainly been evident in the postmortem Fort Hood analysis. Repeatedly the media advised us not to rush to judgment about the motives of Hasan, who, witnesses say, yelled "Allahu Akbar" before he shot the unarmed.

Many commentators were more likely to cite the stresses of hearing patients discuss two wars in Afghanistan and Iraq than Hasan's own apparent extremist beliefs.

In truth, the Fort Hood murders fit into a now familiar pattern of radical Islamic-inspired violence that manifests itself in two principal ways.

First are the formal terrorist plots. Radical Muslims have attempted, in coordinated fashion, to blow up a bridge, explode a train, assault a military base, and topple a high-rise building — in ways al-Qaida terrorist leaders abroad warned us would follow 9/11.

This year alone, three terrorist plots have been foiled.

Najibullah Zazi was indicted for plans to set off a bomb in New York on the anniversary of 9/11.

Daniel Patrick Boyd and Hysen Sherifi were charged with conspiring to murder U.S. military personnel at the Quantico, Va., military base.

Hosam Maher Husein Smadi — a 19-year-old Jordanian in the U.S. illegally — was arrested after being accused of placing what he thought were explosives near a 60-story office tower in Dallas.

In all these cases, the plotter (or plotters) either had ties to terrorists or voiced Islamic-fueled anger at the U.S.

More than 20 other domestic terrorist plots have been stopped by law enforcement agencies since 9/11. On average, in the 98 months since the World Trade Center and Pentagon attacks, a radical Islamic-inspired terrorist plot has been uncovered every four months.

There have also been "lone wolf" mass murderers in which angry radical Muslims sought to channel their frustrations and failures into violence against their perceived enemies of Islam.

Since Sept. 11, several Muslim men have run over innocent bystanders or shot random people at or near military bases, synagogues and shopping malls.

After the initial hysteria died down, we were usually told that such acts were isolated incidents, involving personal "issues" rather than radical Islamic hatred of the U.S. Yet a few examples show that was not quite the case.

The just-executed sniper John Allan Muhammad, who, along with an accomplice, killed 10, voiced approval of Osama bin Laden and radical Islamic violence.

Naveed Afzal Haq is currently on trial for going on a murderous rampage at the Jewish Federation of Greater Seattle building. A survivor said Haq stated his attack was a "personal statement against Jews."

Mohammed Reza Taheri-azar ran over nine students at the University of North Carolina. Officers said he told them afterward he wanted to avenge the deaths of Muslims worldwide.

Omeed Aziz Popal struck 18 pedestrians with his car near a Jewish center in San Francisco. Witnesses say he said, "I am a terrorist," at the scene.

No doubt in each case, experts could assure us that there were extenuating personal circumstances — stresses and mental illnesses that better explain what happened.

Mere mention that such killers typically voiced radical Islamic or virulently anti-Semitic themes often can earn one charges of Islamaphobia, racism or other illiberal biases. Indeed, I expect dozens of angry, accusatory letters in response to this column.

Nevertheless, the facts since 9/11 reveal an undeniable reality.

Every few months either an Islamic-inspired terrorist plot will be foiled, or a young Muslim male will shoot, run down or stab someone while invoking anger at non-Muslims.

In other words, the attack on Fort Hood happened on schedule. It was the rule, not the exception. And something like it will occur again — soon.