But as Stevens met with Benghazi civic leaders, U.S. officials appear to have underestimated the threat facing both the ambassador and other Americans. They had not reinforced the U.S. diplomatic outpost there to meet strict safety standards for government buildings overseas. Nor had they posted a U.S. Marine detachment, as at other diplomatic sites in high-threat regions.

A U.S. military team assigned to establish security at the new embassy in Tripoli, in a previously undisclosed detail, was never instructed to fortify the temporary hub in the east. Instead, a small local guard force was hired by a British private security firm as part of a contract worth less than half of what it costs to deploy a single U.S. service member in a war zone for a year…

Days before the ambassador arrived from the embassy in Tripoli, a Libyan security official had warned an American diplomat that foreigners should keep a low profile in Benghazi because of growing threats. Other Westerners had fled the city, and the British had closed their consulate.