This photo was taken at 20:03, or 2 hours and 11 minutes before the first sirens would have sounded on 13 February, 1945, to alert the Dresdeners to what was coming from this direction.
The target was the Altstadt, or Old City, not for its military value, but for the concentration of dry timber buildings. After the guiding flares, the first waves of bombers dropped high explosives to bust things up, and then the next waves dropped incendiaries to set them afire. 25,000 people died in the resulting firestorm.
Depending on whose wartime propaganda you believed, Dresden was either the heart of European culture and learning, or an armed military camp waiting to derail the coming Russian invasion. Either way, the Dresdeners had deluded themselves that they could sit out the war and reap the benefits of the vicious Nazi renaissance without paying its price. By the end of the war, 2 1/2 months later, they would be thoroughly disabused of that notion.