This unit was initially based at Bernburg until it was moved to Groß Stein, present-day Kamień Śląski in south-western Poland, on 6 August 1939.

[4] StG 77 and its subordinated Jagdgruppe were placed under the command of Wolfram Freiherr von Richthofen's Fliegerführer zbV which became the Fliegerkorps VIII.

[4] According to German plans, Richthofen's forces were to strike into Lesser Poland, toward Kraków, Łódź and Radom in support of the 10th and 14th Armies.

JGr 102, under the command of Hauptmann Gentzen claimed 28 Polish aircraft in aerial combat and a further 50 on the ground.

Colonel Stefan Pawlikowski's Warsaw Pursuit Brigade resisted fiercely but lost 17 percent of its fighting strength on 1 September which rose to 72 over the next five days.

[8] One of JGr 102's missions was providing fighter escort for Ju 87 Stuka dive-bombers in the Bombing of Wieluń.

[9] Gentzen claimed seven victories in two days: on 3 September he shot down a PZL.37 Łoś medium bomber and two PZL P.11 fighters.

[12] JGr 102's parent unit, StG 77 continued to support the invasion, and fought in the Battle of Radom and the Siege of Warsaw.

[13] Johannes Gentzen, the commanding officer, remarked that the Bf 109 pilot's success over Poland depended largely on luck.

On one occasion, he managed to shoot down a Polish fighter, which glided and landed on a heavily camouflaged airfield before it burst into flames while the pilot ran for cover.

According to Glentzen, the group proceeded to strafe the airfield, knocking out five Polish bombers and then firing at a row of haystacks which masked more fighter aircraft.

[17] The Soviet invasion of Poland occurred on 17 September 1939, and Polish resistance to the aggressor nations ended on 6 October.

[20] On one such occasion, on 6 November 1939, Gentzen at the head of 27 Bf 109Ds of JGr 102, patrolled the River Saar, only to meet nine French Hawk H 75As of Groupe de Chasse 11/5 escorting a Potez 63 reconnaissance aircraft of the GR 11/22.

[19][21] Gentzen was summoned to Berlin to explain why JGr 102 lost a 25 percent of its strength to a force approximately one-third of its size.

The automatic constant-speed propeller kept up maximum engine performance/efficiency whereas the Bf 109D pilot had to adjust pitch manually, which caused distractions in a dogfight.

Over-confidence, the experience of Poland, and the spectre of the World War I dogfighting traditions, while speculative, may have led to the JGr 102's defeat.

Five Zerstörergruppen posing as Jagdgruppen (JGr 101, 102, 126, 152 and 176) finally received Messerschmitt Bf 110 heavy fighters in the spring.

The performance of the gruppe, according to RAF Advanced Air Striking Force (AASF) losses, was limited to a single 73 Squadron Hurricane shot down.

[33] On 20 May, as the Panzer Divisions reached the English Channel and completed the encirclement, I./ZG 2 escorted Dornier Do 17s from I./KG 3 as they attacked targets near Abbeville.

I Gruppe was transferred to Bruno Loerzer's air corps and was ordered to escort KG 53 in bombing rail and road traffic between the Seine and Aisne.

Gentzen, commanding I./ZG 2, angered by the persistent attacks, took off to chase a formation of Bristol Blenheims only to crash and die on 26 May 1940.

The Luftwaffe tried to lure RAF Fighter Command into battle by attacking Allied Channel convoys bringing in supplies from abroad and moving materials around the British coast.

[39][40] On 11 August 1940 ZG 2 escorted I and II./KG 54 "Totenkopf" Junkers Ju 88 bombers in an attack on Royal Navy bases at Portsmouth and Weymouth.

[41] ZG 2 engaged further RAF fighter units and claimed an exaggerated 17 Hurricanes and Spitfires shot down for two additional losses.

[51] ZG 2 was supposed to provide escort during one these attacks, and in a breakdown of communications, arrived over the target without their Ju 88s, which had been ordered to stand down.

Flight Lieutenant James Nicholson noticed a Bf 110 circling him suspiciously as he hung in his parachute, he played dead and his act worked.

The Oberkommando der Luftwaffe felt Fighter Command had been worn down, and a massive attack on the British capital would draw out the remaining RAF reserves to be destroyed.

Five ZG 2 crews (three from I. Gruppe) were shot down after encountering strong opposition from the Duxford Wing in an evening attack.

In preparation for the offensive, the German 6th Amy began Operation "Wilhelm", to seize staging areas near Volchansk.

Stab and III/ZG 2 located to Comiso and Bizerta in Italy and North Africa in November 1942 under Luftflotte 2 and then II Fliegerkorps and then Fliegerfuhrer Tunis.