I. Blitzkrieg!

At 0430 hours on Friday, 1 September 1939, three Ju 87B-1 Stukas swept through the early-morning mist towards the Vistula River. Lead by Oberleutnant Bruno Dilley, the Kette from 3./St.G 1 buzzed just inches from the treetops, never higher than thirty feet off the ground. The goal for the crew of these vulture-like aircraft was to destroy a block house at Dirschau on the bank of the Vistula River. This strongpoint protected demolition wires buried on the bank of the Vistula used to blow up three vital bridges in case of invasion. These bridges were essential for the invading German Third Army, enabling it to link up with the Fourth Army and push to Warsaw.
Four minutes later the Kette had reached its target. Oblt. Dilley nosed his machine towards the river bank and screamed towards the target at low altitude. The two accompanying Junkers followed, and seconds later released their deadly payload with uncanny accuracy. As the aircraft climbed upwards explosions rocked the Vistula, severing the demolition wires. A few minutes later a wave of high-flying Dorniers from III./KG 3 Blitz finished off the job. The Second World War had officially begun.
The aerial onslaught of Poland was a carefully planned and executed campaign. Operating in conjunction with the Wehrmacht, the Luftwaffe's role in the blitzkrieg invasion was a four stage process. The first, and most crucial, step was the elimination of the Lotnictwo Wojskowe on the ground and in the air. Once air superiority had been established, medium bombers could shatter roads, railroads, and communications. This served a twofold purpose of both immobilizing the Polish Army and prohibiting it from receiving reinforcements. Then dive-bombers, close support bombers, fighter-bombers, and other light attack aircraft would hit the enemy troops themselves. Finally, aircraft simultaneously attacked factories and cities far behind enemy lines, further restricting the enemy's ability to fight.
The responsibility of attacking airfields and supporting the army in the field was entrusted to Luftflotte 4. Luftflotte 1 was responsible for "Operation Seaside", or the strategic bombing of the Polish capital city. Unfortunately for the Germans the initial main attack against Warsaw was frustrated by foul weather over northern Poland. As a result Luftflotte 4 flew most of the first raids, its first mission directed against Krakow and the nearby Rakowice airbase. Sixty He 111P bombers of I. and III./KG 4 Wever, escorted by twin-engined Bf 110C fighters of I./ZG 76 Haifisch, caught the Polish defenses around Krakow totally by surprise, unloading 48 tons of bombs with impunity on Rakowice airfield below. Two more waves of thirty Stuka dive-bombers from I./St.G 2 Immelmann and one-hundred Do 17Z bombers from I., II., and III./KG 77 made follow up attacks at low altitude, further pulverizing the defenseless airdrome.
Throughout the day similar attacks occurred all over Poland. Twelve main air bases were hit, besides seventy-five forward airfields. For example II./KG 4 Wever bombed Lemberg Airport at Lwów, and after the weather cleared Luftflotte 1 joined in, I./KG 1 Hindenburg raiding Thorn aerodrome and I./KG 53 Legion Kondor hitting Gnesen airfield. Major General J. F. C. Fuller describes a typical German attack mission:

Led by one or more reconnaissance machines, squadrons of nine bombers protected by fighters and flying at an altitude of some 10,000 feet made for their targets. On approaching them they came to about 3,000 feet, and when over the target dropped their bombs in groups of three aircraft at a time. This done, the fighters dived down within a few feet of the ground and machine-gunned any aircraft or personnel to be seen. Sometimes, before the bombing took place, a reconnaissance plane, flying low, would surround the target with a ring of white smoke.

II. The Lotnictwo Wojskowe Fights Back

Despite these tactics, however, only 24 operational Polish combat aircraft were initially destroyed on the ground. The destruction of so few combat aircraft can be attributed to the Poles, who carefully dispersed and hid most of their aircraft during Polish mobilization between 27 and 31 August. In fact most of the aircraft lining the airfields on 1 September were either trainers, civilian aircraft, or obsolete types. Thus the Luftwaffe would encounter determined opposition over the Polish skies after the initial shock of invasion subsided, as little PZL fighters made desperate attempts to repulse the invaders despite their overwhelming numerical inferiority.
The first air battle occurred shortly after the initiation of hostilities. Two P.11c fighters of 121 Eskadra took off from Balice airdrome to intercept the He 111Ps of KG 4 that were attacking Krakow (as related above), piloted by Kapitan Mieczyslaw Medwecki and Podporucznik Wladislaw Gnys. Still climbing the duo was attacked by the Junkers dive-bombers of I./St.G 2, Unteroffizier Frank Neubert shooting down Kap. Medwecki in flames. Ppor. Gnys attempted to engage the Stukas, but stalled before he could confirm a kill. After the encounter he climbed to 3,600 feet (1,097 meters), spotting the Dorniers of KG 77 returning from Krakow below him. He dived on the formation, peppering one Dornier with machine gun fire before engaging another. Both machines crashed in the nearby village of Zurada. On his way home Gnys engaged a final Heinkel, but was unable to confirm a kill.
The Luftwaffe's airfield campaign continued over the next few days, though never with any conspicuous success. On the second day of hostilities eighty-eight He 111Ps of I., II., and III./KG 4 Wever left three airdromes near Dublin in flames, with a follow-up attack by strafing Bf 110Cs of I./ZG 76 Haifisch. All of the eleven aircraft destroyed were trainers, however. Later that day I./ZG 76 strafed Lodz airfield, to be intercepted by PZLs of Dyon III/6. Diving out of the sun, the six P.11s dispatched two Messerschmitts, before losing two of their own number.