Senators ask Mattis for more information on Niger attack

“It’s too early to say. That’s exactly the questions we should be asking ourselves. In war you fail, you make mistakes and the whole goal is to learn from your mistakes and not repeat them.”

That will likely prompt a debate in Congress over the broader counterterrorism strategy and the need for an updated Authorization for the Use of Military Force or "AUMF" – a debate which certain members have called for repeatedly over the years but which has largely been stagnant.

The counterterrorism fight is going to shift to Africa more and more, Graham said.

“You're going to see more actions in Africa, not less. You’re going to see more aggression by the United States towards our enemies, not less. You're going to have decisions being made not at the White House but in the field. And I support that entire construct.”

McCain met separately with Mattis, and after the meeting, with the secretary at his side, McCain said he and Mattis talked about the need for his committee to receive more information about the Niger ambush.

"I felt that we were not getting sufficient amount of information and we are clearing a lot of that up," McCain said.

Mattis added, "We can do better at communication. We can always improve on communication and that's exactly what we'll do.

Ahead of his meeting with McCain, Mattis was asked if the threat of the subpoena prompted him to meet with the senator. "Are you kidding me?" Mattis said to the reporter.

Mattis said the president is "kept fully informed' on the Niger ambush, but declined to say how often he is briefed about the timeline.