Story highlights David Andelman: It's vital that the Pentagon investigation uncover why American soldiers were vulnerable to an ambush in western Niger

He says the Trump administration travel ban needlessly alienated Chad, which has been a partner in fighting militants in Niger's eastern region

David A. Andelman, a contributor to CNN and columnist for USA Today, is the author of "A Shattered Peace: Versailles 1919 and the Price We Pay Today." He formerly was a foreign correspondent for The New York Times in Asia and Europe, and Paris correspondent for CBS News. Follow him on Twitter @DavidAndelman. The views expressed in this commentary are his.

(CNN) Just how was it left to Nigerien troops and French helicopters to find and fetch the bodies of our heroic service members killed in Niger?

Why did they apparently have so little air or intelligence muscle to protect them in the first place? We could get a final answer after the completion of a Benghazi-style after-action probe by the United States Africa Command, or AFRICOM.

At a Pentagon briefing Monday afternoon, the chairman of the Joint Chief of Staff suggested some of the answers, if only the most basic timeline and structure of the operation. It is still, General Joseph Dunford suggested, too early to assess the full context or broader timeline. What already seems likely is that at least some blame could lie with those who set in motion a bewildering series of actions.

The broader timeline begins in the region on September 24, when the Trump administration suddenly and inexplicably added Chad to the list of countries whose citizens would be included in the latest iteration of the president's travel ban. Chad and its leaders were utterly blindsided as there was no sense whatsoever that this nation has harbored or even encouraged terrorists -- certainly no more culpable than such nations as Iraq, Pakistan, Sudan, or for that matter Chad's neighbors Mali, Niger and Nigeria, none of which were included on this list.

Au contraire, Chad's troops have for some time served as an effective ally in the region -- the best fighting force deployed in nearby Niger and Mali, with the best intel and best-trained warriors. They were the best because they were trained by the French and its redoubtable Foreign Legion. I know, because I was there in Chad in 1983 when the French had to send in their forces to backstop them when they thought Libya's Moammar Gadhafi might invade from the north.