KABUL, Afghanistan — Seven minutes after a truck bomb went off in the Afghan capital on Tuesday, the first teams from Kabul Ambulance Service reached the scene of devastation.

Right away, they knew the attack was bad, but not that it would turn out to be the deadliest in the Afghan capital in 15 years of war.

The teams radioed in the extent of the carnage, activating the small department’s contingency plan: All of its 15 vehicles and staff from across the city were dispatched to the bomb scene, behind the compound of an elite security force along the Kabul River.

Mechanics got behind the wheel and clerks took on nursing duties, ferrying the wounded to the city’s hospitals for hours.