1.) At about 9:45 p.m., a large tanker truck and an accompanying white car drive into the parking lot of a nearby park in a clockwise direction. The lot, which is unguarded and open to anyone, abuts the Khobar Towers complex, where American, British and French troops are housed.

2.) Three U.S. Air Force offi cers, manning a guard post only recently created atop Khobar Building 131, are the first to notice something peculiar as the truck and car roll onto 31st Street, running along the security fence.

3.) Shortly after 9:45 p.m., one of the officers, Sgt. Alfredo Guerrero, radios the base’s security force about a likely terrorist attack when the truck backs closer to the hedge and its driver jumps into the accompanying car, which speeds away from the truck and out of the lot.

4.) Guerrero and the other guards scramble into the building, and go door to door warning residents. Fire alarms cannot be used because they could lead soldiers out of the building and tow, the bomb. The top two floor of the building have been alerted when the bomb goes off about three minutes later.

5.) Only minutes after the explosion, the base’s medical clinic is seeing its first casualties. Medical technicians arrive at the clinic ready to rush to Building 131. But before they have a chance, they are met by soldiers carrying the injured, covered with homemade bandages and tourniquets, to makeshift triages.

Even before last week’s tragedy, the security of the 2,200 soldiers at the Dhahran base was an issue. Recent preventive measures:

The gulf’s resources make it worth protecting. A look at U.S. troops and oil in the region:

Mostly air force. The single biggest group-some 2,200 soldiers-are based in Dhahran.

The army has a brigade’s worth of equipment-roughly 30,000 pieces of combat and combat-support hardware including tanks. There are plans to double this number. The air force has 24 A-10s here.

The tiny island nation is headquarters of the navy’s Fifth Fleet.

Marines are conducting exercises here and until a week ago the air force was flying over Iraq from bases here. Diego Garcia: This base, on a cluster of coral reefs, acts as a supply point for U.S. gulf deployments.

A carrier group operates in the Indian Ocean (8 vessels, 67 aircraft); a marine assault group is in the Red Sea (6 vessels). Other combat and support ships are deployed in the Arabian Sea (12 vessels).