With headlines about Ebola, the Secret Service and Islamic State terrorists monopolizing the news, some Americans may have missed an extraordinarily significant report this week.

On Sept. 30, U.S. and Afghan officials signed an agreement allowing American combat troops to be stationed in Afghanistan after Dec. 31. It remains to be seen how many troops President Barack Obama will leave there.

U.S. combat troops were pulled out of Iraq at the end of 2011, because that country’s rulers would not sign a similar agreement. Some analysts have said Obama did not push hard enough for it.

Almost beyond any doubt, a contingent of U.S. combat troops in Iraq could have stopped, or at least slowed, conquest of a large section of that country by the Islamic State. The president and some of his supporters insist that would not have been the case. His critics, however, strongly dispute that conclusion. They argue that leaving U.S. combat troops in Afghanistan could serve as a bulwark against re-conquest of that nation by the Taliban.

No one wants to put Americans in peril unnecessarily.

But plainly, the mistake made in Iraq should not be repeated.