'Clarion' was an Allied major bombing offensive designed to destroy German surface communications and morale (22/23 February 1945).

Nearly 9,000 Allied sorties attacked targets across Germany in effort to destroy any and all means of transportation available. The targets included railway marshalling yards, level crossings and signal boxes, bridges, canal locks and other elements of the German transport infrastructure.

The primary objective was the concentration of all the available Allied air power over Germany for attacks on all the military communications and transportation targets which had so far escaped damage. Most of these targets were located in small towns which had not been bombed up to this time, and it was hoped that the great geographical as well as evident air power implications of the operation would emphasise to the German people the hopelessness of their position. More directly, the offensive targeted 200 locations in the German communications network whose use would have facilitated the German response to 'Veritable' and 'Grenade'.

Typical of the 'Clarion' programme was the attack of 22 February on the marshalling yard in Hildesheim. As a result of the good weather, with excellent visibility, the marshalling yard was severely impaired and the city itself received considerable damage: 102 houses were completely destroyed, 106 houses and two churches were badly damaged, and some 250 persons were killed.

Hildesheim was also the target for air attack on three dates in March. On 3 March the city was an alternate target when Braunschweig was bombed, and 583 bombs were dropped on Oststadt, a residential area in the eastern part of the city. Some 51 houses were destroyed, 58 suffered severe damage and 22 were slightly damaged, and 52 persons were killed.

On 14 March elements of Major General Howard M. Turner’s 1^st Air Division of the VIII Bomber Command bombed several targets in the area around Hanover. Among these were the Vereinigte Deutsche Metallwerke and, once again, the marshalling yard. While the marshalling yard was hit hard again and disabled for several days, the bombers missed VDM and instead bombed the Senking metal works, completely destroying the factory. About 150 persons were killed, including 60 prisoners of war. In the city itself, 18 houses were completely destroyed, 20 suffered severe damage, and 109 were slightly damaged.

On 22 March Hildesheim was the key target for Allied bombers. British and Canadian aircraft were ordered 'to destroy [the] built up area with associated industries and railway facilities'. At 14.00 about 250 bombers started the attack. In the following 15 minutes, they dropped 438.8 tons of HE and 624 tons of incendiary bombs. Almost 74% of Hildesheim’s buildings were destroyed or damaged during the attack, including nearly the whole of the city’s mediaeval centre, which was almost totally levelled. About 1,500 civilians were killed in the three attacks of March.