WASHINGTON (AP) — The U.S. special forces unit ambushed by Islamic militants in Niger didn't call for help until an hour into their first contact with the enemy, the top U.S. general says, conceding many questions linger about the assault that killed four American troops and triggered a political brawl.

Marine Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, told reporters the American people and the fallen soldiers' families deserve answers about the deadly ambush in the West African nation. But Dunford said Monday that he still lacks many details about how the attack unfolded.

At...