'Millennium II' was a British 'Thousand Force' bombing raid on Bremen by Air Marshal Sir Arthur Harris’s RAF Bomber Command in succession to 'Millennium' (i) and 'Arabian Nights' (25/26 June 1942).

Bremen was the third target for the 'Thousand Force', although in fact only 960 Bomber Command aircraft took off. Every type of aircraft in service with Bomber Command was represented, including the Douglas Boston and de Havilland Mosquito twin-engined light bombers of Air Vice Marshal A. Lees’s No. 2 Group, which had been used only for day operations up to this time. The force therefore comprised 472 Vickers Wellington two-engined medium, 124 Handley Page Halifax four-engined heavy, 96 Avro Lancaster four-engined heavy, 69 Short Stirling four-engined heavy, 51 Bristol Blenheim two-engined light, 50 Handley Page Hampden two-engined medium, 50 Armstrong Whitworth Whitley two-engined medium, 24 Boston, 20 Avro Manchester two-engined heavy and four Mosquito machines. This was the most mixed force Bomber Command ever dispatched on a single raid.

After Prime Minister Winston Churchill had intervened and insisted that the Admiralty allow Air Chief Marshal Sir Philip Joubert de la Ferté's RAF Coastal Command to participate in this raid, another 102 aircraft (Lockheed Hudson two-engined light and Wellington machines) of Coastal Command were sent to Bremen, but official records class this as a separate raid as the aircraft were not under Bomber Command’s control. Another five aircraft provided by Air Marshal Sir Arthur Barrett’s Army Co-Operation Command, were also added to the force.

The final number dispatched was therefore 1,067 aircraft, which made this a larger raid than 'Millennium'. Parts of the force were allocated to specific targets in Bremen. The entire effort of Air Vice Marshal W. A. Coryton’s No. 5 Group (142 aircraft) was instructed to bomb the Focke-Wulf factory; 20 Blenheim aircraft were allocated to the A.G. Weser shipyard; the Coastal Command aircraft were to bomb the Deschimag shipyard; and all other aircraft were to carry out an area attack on the town and docks.

The tactics used in this raid were basically similar to those of the earlier 'Thousand Force' raids except that the bombing period was now cut to 65 minutes.

Bremen, near the mouth of the Weser river, should have been an easy target to find and the inland penetration of the German night fighter belt was only shallow. There were doubts about a band of cloud which lay across the Bremen area during the day, but this was being pushed steadily eastward by a strong wind. Unfortunately the wind dropped in the evening and the bomber crews found the target completely covered for the whole period of the raid. The limited success which was gained was the result wholly of the use of the 'Gee' radio navigation system, which made it possible for the leading crews to start fires, onto whose glow many aircraft of later waves bombed. Some 696 Bomber Command aircraft were able to claim attacks on Bremen.

The results in general terms were not as dramatic as in 'Millennium', but much better than those of the second 'Thousand Force' raid on Essen. Bremen reported a strengthening wind at the time of the raid which fanned the many fires started throughout the city, increased the extent of the damage and left whole areas of housing in ruins: 572 houses were completely destroyed and 6,108 damaged (more than 90% of these in the southern and eastern quarters of the city’s four air-raid areas), and the casualties were 85 persons killed, 497 injured and 2,378 bombed out. On the industrial side, the German record stated that the British plan to destroy the Focke-Wulf factory and the shipyards was not successful, although an assembly shop at the Focke-Wulf factory was completely flattened by a 4,000-lb (1814-kg) bomb dropped by a Lancaster of No. 5 Group. Another six buildings at this factory were seriously damaged and 11 lightly damaged. Damage was also experienced by four important industrial firms (the Atlas Werke, the Vulkan shipyard, the Norddeutsche Hütte and the Korff refinery) and two large dockside warehouses. The report concluded with the estimate put forward by the senior local air-raid official at the time that only 80 British bombers had attacked Bremen, and the German claimed 52 of them shot down.

Bomber Command’s actual losses were 48 aircraft including four which came down in the sea near England and from which all but two crew members were rescued. This was a new record loss, and represented exactly 5% of the Bomber Command aircraft dispatched. The heaviest casualties were suffered by the operational training units of Air Commodore H. S. P. Walmsley’s No. 91 Group, which lost 23 of the 198 Whitley and Wellington aircraft provided by that group, representing a loss of 11.6%. The reasons for this may be the fact that OTUs were usually equipped with old aircraft retired from front-line squadrons, that the Bremen raid involved a round trip 200 miles (320 km) longer than the Köln and Essen raids, and that extra time had been taken up in searching for the target in the cloudy conditions of that night. Coastal Command also lost five aircraft.