'Coldwater' was the British response to intelligence about the imminent 'Mondscheinsonate' German air attacks on Birmingham and Coventry (14/15 November 1940).

The operation involved conventional countermeasures such as jamming of the German radio navigation aids, 110 fighter patrols, enhanced anti-aircraft artillery preparations and bombing.

This last was undertaken by Air Marshal Sir Richard Peirse’s RAF Bomber Command, and targeted 27 German bomber airfields in occupied Belgium, France (especially that of Hauptmann Kurt Aschenbrenner’s Kampfgruppe 100 pathfinder unit at Vannes) and the Netherlands, as well as a number of German towns and cities including Berlin, Gelsenkirchen, Magdeburg, Hamburg, Essen, Köln, Duisburg, Kiel and Wilhelmshaven.

Bombing raids during this period took place on several nights. On 12/13 November 77 aircraft were despatched against many targets, the largest single attack being that by 24 Vickers Wellington twin-engined medium bombers on Gelsenkirchen, though only six of the aircraft reached that target. Because of the adverse winter weather, in fact only 19 of all the aircraft despatched bombed their primary targets. The British losses were just one Armstrong Whitworth Whitley twin-engined medium bomber.

On 13 November nine Bristol Blenheim twin-engined light bombers were despatched, but only two of these bombed targets in France and there were no losses.

On 13/14 November 72 Handley Page Hampden twin-engined medium bombers, Whitley medium bombers and Wellington heavy bombers were despatched against five targets: one Hampden was mistakenly shot down by a Supermarine Spitfire single-engined fighter soon after take-off, and another Hampden as well as a Whitley were lost. Only 15 of the aircraft reached their primary targets.

During the evening of 14 November 35 Blenheim light bombers were despatched to attack known Luftwaffe bomber airfields in France and Belgium on the basis of the 'Ultra' information about 'Mondscheinsonate', but only 10 of the aircraft carried out attacks on these airfields with results recorded as 'generally unobserved'. All of the Blenheim attackers returned safely, but 'Mondscheinsonate' duly took place on Coventry.

On 14/15 November 82 Hampden, Wellington and Whitley bombers were despatched, the largest element being sent to attack Berlin, but only 25 of these 50 aircraft reported reaching the German capital.

Raids on the airfields at Schiphol and Soesterberg in the German-occupied Netherlands were specifically designed to frustrate the suspected German bombing raid on England. Other efforts of the night included aerial minelaying off Best and Lorient by three Hampden bombers. The British losses for the night were 10 aircraft (four Hampden, four Whitley and two Wellington bombers), which was the heaviest British night loss of the war so far.

On 15/16 November Hampden, Wellington and Whitley bombers were despatched against Hamburg in two waves eight hours apart. On their return, the crews reported good bombing conditions, and in Hamburg 68 fires were started and what was for the time heavy damage was caused at the Blohm & Voss shipyard. The German casualties were 26 people killed, 102 injured and 1,625 bombed out. This was almost certainly the most successful Bomber Command raid of the war so far. During the same night 56 Blenheim, Wellington and Whitley bombers continued raids on Luftwaffe bomber airfields in German-occupied countries. All the British operations on this night were free from loss.

On 16 November six Blenheim bombers were sent to northern Germany, but the four aircraft which managed to bomb attacked targets not in Germany. The attackers suffered no loss.

On 16/17 November Hamburg was again the target, with 130 bombers launched against four targets in this north German port city. The weather conditions were unfavourable, however, and only 60 aircraft reported bombing Hamburg, with another 25 attacking alternative targets. In Hamburg six fires were started, and the German casualties were two persons killed, 36 injured and 786 bombed out. Some 50 miles (80 km) to the north of Hamburg, in Kiel five people were killed and 16 injured on this night. The British losses were Wellington and one Blenheim, and another five bombers crashed in England. The same night also saw operations by another 15 aircraft, of which three were involved in aerial minelaying and the other 12 in bombing airfields, both without loss.