The RAF, at the request of the Danish resistance, came up with a plan to conduct a low-level bombing raid on the Gestapo HQ in Copenhagen. After several delays, it was conducted on March 21, 1945.
The target was the Shell Oil Company building, or Shellhus, which had been taken over by the Gestapo.
"In the fall of 1944 several cells were established on the top floor to minimize transportation of prisoners from Vestre faengsel (a large prison in Copenhagen) to interrogation and torture in the Shellhus.
By the end of 1944 the resistance-movement in Copenhagen was in danger of being rolled up by the Gestapo. Many of the leaders had been arrested and a lot of material was filed in the archives of the Shellhus. Leading members of the resistance-movement requested an attack by air on the Shellhus via SOE in London. By December 1944 the plan was ready, but the German counter attack in the Ardennes stopped the attack.
By the end of january 1945 the RAF was ready, but the attack was postponed probably due to the weather. In the middle of March the situation for the resistance-movement became intolerable. A desperate telegram was sent to London beggin for an attack: If the resistance-movement was at all important the RAF had to attack at all costs."
Danish history site detailing the raid
"On the morning of 21 March 1945, a special force of Mosquitos from No 140 Wing took off from an aerodrome in England to attack the Gestapo Headquarters in Copenhagen.
Before the attack could be carried out, several weeks of careful planning were necessary. Two large scale models, one representing the city, and the other the Gestapo building, were used to brief the pilots in every detail - trees, lake and houses - were pointed out on these models which took 340 man hours to construct."
RAF website detailing the raid
British Mustang photgraphed during the attack.
British Mosquito bombers over Copenhagen
Shellhus folowing the attack
The raid had success in disrupting German operations, but at a cost.
"The raid was carried out at rooftop level. In the course of the initial attack, a Mosquito hit a lamp post, damaging its wing, and the plane crashed into the Jeanne d'Arc School, about 1.5 km (0.93 mi) from the target. Several bombers in the second and third wave attacked the burning school, thinking it was their target, and as a result 86 schoolchildren died in the school, along with 18 adults, including many nuns.
On the following day, a reconnaissance plane surveyed the target to assess the results. The damage was heavy, with the west wing of the six-story building reduced to nearly ground level. The Danish underground supplied a photograph showing the building burning from end to end.
The raid had succeeded in destroying Gestapo headquarters and severely disrupting Gestapo operations in Denmark, as well as allowing the escape of 18 prisoners of the Gestapo. Fifty-five German soldiers, 47 Danish employees of the Gestapo, and eight prisoners died in the headquarters itself. Four Mosquito bombers and two Mustang fighters were lost, and nine airmen died on the Allied side."
Wiki article on Operation Carthage
Memorial to the civilians killed at the school.