The first hour was defined by that initial, critical mistake: the failure to identify the location of the fire, and by the delay that followed.

The second hour was dominated by a sense of helplessness. As people raced to the building, waves of shock and mourning for one of the world’s most beloved and recognizable buildings, amplified over social media, rippled in real time across the globe.

That Notre-Dame still stands is due solely to the enormous risks taken by firefighters in those third and fourth hours.

Disadvantaged by their late start, firefighters would rush up the 300 steps to the burning attic and then be forced to retreat. Finally, a small group of firefighters was sent directly into the flames, as a last, desperate effort to save the cathedral.