Only 12 Ju 88s saw action in Poland. The unit Erprobungskommando 88 (Ekdo 88) was responsible for testing new bomber designs and their crews under hostile conditions. They selected 12 aircraft and their crews and attached them to 1./Kampfgeschwader 25. As a result of its small operational numbers, the type made no impact.
Battle of Norway
The Luftwaffe committed II./Kampfgeschwader 30 to the campaign under X. Fliegerkorps for Operation Weserübung. The unit was equipped with Ju 88s and engaged Allied shipping as its main target. On 9 April 1940, Ju 88s of KG 30 dive-bombed, in cooperation with high-level bombing Heinkel He 111s of KG 26, and helped damage the battleship HMS Rodney and sink the destroyer HMS Gurkha. However, the unit lost four Ju 88s in the action, the highest single loss of the aircraft in combat throughout the campaign.
Battle of France
The Luftwaffe's order of battle for the French campaign reveals all but one of the Luftwaffe's Fliegerkorps (I. Fliegerkorps) contained Ju 88s in the combat role. The mixed bomber units, including the Ju 88, of Kampfgeschwader 51 (under the command of Luftflotte 3) helped claim between 233 and 248 Allied aircraft on the ground between 10–13 May 1940. The Ju 88 was particularly effective at dive-bombing. Between 13–24 May, I. and II./KG 54 flew 174 attack against rail systems, paralysing French logistics and mobility. On 17 June 1940, Junkers Ju 88s (mainly from Kampfgeschwader 30) destroyed a "10,000 tonne ship", the 16,243 grt ocean liner RMS Lancastria, off Saint-Nazaire, killing some 5,800 Allied personnel. Some 133 Ju 88s were pressed into the Blitzkrieg, but very high combat losses and accidents forced a quick withdrawal from action to re-train crews to fly this very high-performance aircraft. Some crews were reported to be more scared of the Ju 88 than the enemy, and requested a transfer to an He 111 unit. By this time, major performance deficiencies in the A-1 led to an all-out effort in a major design rework. The outcome was a longer, 20.08 m (65 ft 10 1/2 in) wingspan, from extended rounded wing tips that had already been standardised on the A-4 version, that was deemed needed for all A-1s; thus the A-5 was born. Surviving A-1s were modified as quickly as possible, with new wings to A-5 specifications.
Battle of Britain
The Battle of Britain proved very costly. Its higher speed did not prevent Ju 88 losses exceeding those of its Dornier Do 17 and Heinkel He 111 stablemates, despite being deployed in smaller numbers than either. Ju 88 losses over Britain in 1940 amounted to 303 aircraft between July and October 1940. Do 17 and He 111 losses for the same period amounted to 132 and 252 machines destroyed respectively.
However, of all the losses suffered by the Ju 88 at that time, a notable number were due to the tricky behavior of the plane, especially when compared to the proven He 111, and to the crews' lack of experience on the type - many having converted to the Ju 88 only shortly before. For instance, of the 39 losses recorded for July 1940, only 20 were due to enemy action, the others being written off in training accidents, crashes or malfunctions over the mainland Europe. A series of field modifications were made to make the Ju 88 less vulnerable, including the replacement of the single MG 15 rear machine gun by a twin-barreled MG 81Z machine gun, and the fitting of additional cockpit armour.
One notable incident involved ground fighting between the crew of an A-1 and soldiers from the London Irish Rifles during the Battle of Graveney Marsh on 27 September 1940. It was the last action between British and foreign military forces on British mainland soil.
It was during the closing days of the Battle of Britain that the flagship Ju 88 A-4 went into service. Although slower yet than the A-1, nearly all of the troubles of the A-1 were gone, and finally the Ju 88 matured into a superb warplane. The A-4 actually saw additional improvements including more powerful engines, but, unlike other aircraft in the Luftwaffe, did not see a model code change. The Ju 88 C-series also benefited from the A-4 changes, and when the Luftwaffe finally did decide on a new heavy fighter, the Ju 88C was a powerful, refined aircraft.
By the summer of 1941, most of the units equipped with the Dornier Do 17 were upgrading to the Ju 88. With a few exceptions, most of the German bomber units were now flying the He 111 and Ju 88. The Ju 88 was to prove a very capable and valuable asset to the Luftwaffe in the east. The Ju 88 units met with instant success, attacking enemy airfields and positions at low level and causing enormous losses for little damage in return. 3./Kampfgeschwader 3 attacked Pinsk airfield in the morning of the 22 June 1941. It caught, and claimed destroyed, 60 Soviet bombers on the ground. The 39 SBAP Regiment of the 10 Division SAD actually lost 43 Tupolev SBa and five Petlyakov Pe-2s. Ju 88s from Kampfgeschwader 51 destroyed over 100 aircraft after dispatching 80 Ju 88s to hit airfields. In general the Soviet aircraft were not dispersed and the Luftwaffe found them easy targets. A report from the Soviet 23rd Tank Division of the 12th Armoured Corps described a low-level attack by Ju 88s on 22 June, resulting in the loss of 40 tanks. However, the Ju 88s were to suffer steady attritional losses. At 0415 on 22 June 1941, III./KG 51 attacked the airfield at Kurovitsa. Despite destroying 34 Polikarpov I-153s, the Ju 88s were intercepted by 66 ShAP I-153s. Six Ju 88s were shot down before the German fighter escort dealt with the threat. By the end of the first day of the campaign, Ju 88 losses amounted to 23 destroyed.
Due to the lack of sufficient numbers of Ju 87 Stukas, the Ju 88 was employed in the direct ground support role. This resulted in severe losses from ground fire. Kampfgeschwader 1, Kampfgeschwader 76 and Kampfgeschwader 77 reported the loss of 18 Ju 88s over enemy territory on 23 June. KG 76 and KG 77 reported the loss of a further four Ju 88s, of which 12 were 100% destroyed.
In the north, the VVS North-Western Front lost 465 aircraft on the ground, 148 of them bombers, to the Ju 88s of KG 1. A further 33 were damaged. Out of a total of 1,720 aircraft deployed by the VVS Northern Front on 22 June, it lost 890 and a further 187 suffered battle damage in eight days. The Ju 88s units helped virtually destroy Soviet airpower in the northern sector.
Again, the Ju 88 demonstrated its dive-bombing capability. Along with He 111s from KG 55, Ju 88s from KG 51 and 54 destroyed some 220 trucks and 40 tanks on 1 July, which helped repulse the Soviet South Western Front's offensive. The Ju 88s destroyed most rail links during interdiction missions in the area, allowing Panzergruppe 1 to maintain the pace of its advance.
Ju 88 units operating over the Baltic states during the battle for Estonia inflicted severe losses on Soviet shipping, with the same dive-bombing tactics used over Norway, France and Britain. KGr 806 sank the Soviet destroyer Karl Marx on 8 August 1941 in Loksa Bay Tallinn. On 28 August the Ju 88s had more success when KG 77 and KGr 806 sank the 2,026 grt steamer Vironia, the 2,317 grt Lucerne, the 1,423 grt Atis Kronvalds and the ice breaker Krisjanis Valdemars (2,250 grt). The rest of the Soviet "fleet", were forced to change course. This took them through a heavily mined area. As a result, 21 Soviet warships, including five destroyers, struck mines and sank. On 29 August, the Ju 88s accounted for the transport ships Vtoraya Pyatiletka (3,974 grt), Kalpaks (2,190 grt) and Leningradsovet (1,270 grt) sunk. In addition, the ships Ivan Papanin, Saule, Kazakhstan and the Serp i Molot were damaged. Some 5,000 Soviet soldiers were lost.
On 2 December 1943, 105 Ju 88 A-4s, armed with bombs and motobomba circling torpedoes, attacked the Allied-held port of Bari, Italy. The attacking force achieved complete surprise and sunk over 20 Allied ships in the overcrowded harbour, including the U.S. Liberty ship John Harvey, which was carrying mustard gas. About 1,000 people were killed and another 1,000 wounded; many fatalities and injuries were as a result of the release of mustard gas. The attacking force lost one aircraft; the Allies had not assigned any fighters to guard Bari as they thought the Luftwaffe incapable of striking in this strength at this stage of the war. The port was completely closed for three weeks from the damage of the raid, and only resumed full operation in February 1944.
Finnish Air Force
In April 1943, as Finland was fighting its Continuation War against the USSR, the Finnish Air Force bought 24 Ju 88s from Germany. The aircraft were used to equip No. 44 Sqn which had previously operated Bristol Blenheims, but these were instead transferred to No. 42 Sqn. Due to the complexity of the Ju 88, most of 1943 was used for training the crews on the aircraft, and only a handful of bombing missions were undertaken. The most notable was a raid on the Lehto partisan village on 20 August 1943 (in which the whole squadron participated), and a raid on the Lavansaari air field (leaving seven Ju 88 damaged from forced landing in inclement weather). In the summer of 1943, the Finns noted stress damage on the wings. This had occurred when the aircraft were used in dive bombing. Restrictions followed: the dive brakes were removed and it was only allowed to dive at a 45-degree angle (compared to 60-80 degrees previously). In this way, they tried to spare the aircraft from unnecessary wear.
One of the more remarkable missions was a bombing raid on 9 March 1944 against Soviet Long Range Aviation bases near Leningrad, when the Finnish aircraft, including Ju 88s, followed Soviet bombers returning from a night raid on Tallinn, catching the Soviets unprepared and destroying many Soviet bombers and their fuel reserves, and a raid against the Aerosan base at Petsnajoki on 22 March 1944. The whole bomber regiment took part in the defence against the Soviets during the fourth strategic offensive. All aircraft flew several missions per day, day and night, when the weather permitted.
No. 44 Sqn was subordinated Lentoryhmä Sarko during the Lapland War (now against Germany), and the Ju 88s were used both for reconnaissance and bombing. The targets were mostly vehicle columns. Reconnaissance flights were also made over northern Norway. The last war mission was flown on 4 April 1945.
After the wars, Finland was prohibited from using bomber aircraft with internal bomb stores. Consequently, the Finnish Ju 88s were used for training until 1948. The aircraft were then scrapped over the following years. No Finnish Ju 88s have survived, but an engine is on display at the Central Finland Aviation Museum, and the frame structure of a German Ju 88 cockpit hood is preserved at the Finnish Aviation Museum in Vantaa.