Kenyans on the bus stopped by armed men at dawn on Saturday knew they were in trouble when their assailants demanded each recite the Shahada, part of Islamic scripture. Those who could not were taken off the bus and told to lie down in a line.

Then two men went down the line, shooting men and women at close range. Twenty-eight were murdered.

Members of the Al-Shabab group – described not as terrorists but as “Somalia’s Islamic extremist rebels” by The Associated Press – conducted the massacre.

How many Americans know the name Al-Shabab? How many have ever heard of the al-Nusra Front, the Haqqani Network or Ansar al-Sharia?

All are major Islamic terrorist organizations. There are dozens of others recognized by countries throughout the world.

How many Americans recoil in anger and perhaps fear at hearing the name Boko Haram? That is the Islamic terrorist group in Nigeria in the news frequently, including several months ago when it captured scores of girls and took them into captivity.

Islamic terrorism is much more widespread and in some places, active than most Americans realize. Killing Osama bin Laden merely eliminated one major terrorist villain. It did little or nothing to curb Islamic terrorism worldwide.

Former President George W. Bush, under whom the formal war on terrorism began, warned it might take decades. President Barack Obama seems slowly to be coming to that realization.

However long it takes, this is a war that must be won.