By the fourth day of the campaign, the Luftwaffe had shifted its priorities. German air power was finally being committed in strength to operations south of Belgium and in north-eastern France. The period during which air operations had been largely concentrated on northern and central Belgium had come to an end. Instead, the bulk of the tactical air forces was redirected towards the Meuse sector, where German armoured formations were emerging from the Ardennes and preparing to force a decisive breakthrough.
The Antwerp region remained an area of operational importance, but Zeeland no longer ranked among the Luftwaffe's primary objectives. The enormous concentration of tactical aircraft over the Meuse absorbed resources that were needed elsewhere. At the same time, the remaining few (already battered) bomber units of Luftflotte 2 had been assigned to support the operational sectors of X Army Corps and XXVI Army Corps.
As a result, bomber activity over Zeeland was comparatively limited on 13 May. Instead, the skies were increasingly dominated by German fighter aircraft. Although their destructive power was less dramatic than that of the bombers, their persistent presence ensured that Allied troops remained under constant observation and harassment throughout the day.
At approximately 0400 hours, shortly after the break of daylight, Haamstede Air Force Base came under a sustained strafing attack by around twenty Messerschmitt Bf 109 fighters, probably of Jagdgeschwader 26 (JG 26). The assault lasted for nearly an hour and inflicted considerable damage on the airfield. All aircraft present, with the exception of a single Fokker C.V biplane, were damaged, while five aircraft were completely destroyed.
The nearby anti-aircraft battery did not engage the low-flying attackers. Its commander considered such action tantamount to suicide, as the exposed gun positions would almost certainly have attracted immediate retaliation. As he reportedly remarked, suicide was not in accordance with regulations. Despite the intensity of the attack, only one serviceman was killed.
Later that afternoon, orders were received to evacuate the airfield and reassign its personnel to coastal defence duties. To prevent its further use, the landing area was deliberately rendered unserviceable. The ground was ploughed up, and vehicles, carts, and other obstacles were placed across the runways.
With these measures, Haamstede Air Force Base effectively ceased to exist as an operational airfield. At least under Dutch control, its role in the campaign had come to an end. During the following occupation the Germans would make extensive use of the airfield and expand it considerably.
Flushing Air Force Base once again came under attack from German fighter aircraft. Yet an even greater threat emerged during the course of the day - not from the air, but from within the ranks of the defenders themselves.
Rumours began to circulate that German troops had already landed on Walcheren and were advancing towards Flushing. Panic spread rapidly. Civilians were suspected of signalling to the enemy with lights from their homes, while innocuous laundry hanging from washing lines was interpreted as coded messages for German forces. As anxiety mounted, rumours multiplied and took on a life of their own. Only towards the evening did their disruptive effect begin to subside. Officers worked tirelessly throughout the day in an effort to restore order and calm their men.
Meanwhile, the 16th Anti-Aircraft Battery at Oost-Souburg was repeatedly confronted by German aircraft passing overhead. The battery's heavy Vickers 75 mm anti-aircraft guns faced a growing logistical problem: ammunition was becoming scarce. Since the German capture of the Moerdijk bridges had severed the overland connection with Fortress Holland, replenishment from the main ammunition depots in the north was no longer possible. As no significant reserves of anti-aircraft ammunition had been stockpiled in the south-western Netherlands, the available ammunition had to be carefully rationed.
Despite these restrictions, the Dutch air defences achieved a notable success. A Messerschmitt Bf 110 C-2 of 5./ZG 1 was shot down over Flushing and crashed near the town's railway station. Both members of the crew were killed in the wreckage, including Hauptmann Küpers, the German squadron commander..
On 13 May, Luftwaffe activity over Zeeland was noticeably reduced for the reasons outlined earlier. The Allied air forces, however, proved far more active and were quick to exploit the temporary easing of German air superiority. French and British fighters were observed throughout the south-western Netherlands, and considerable efforts were made to provide air cover for the French Seventh Army as it repositioned in western North Brabant and around Antwerp. Air activity was particularly intense during the morning hours.
A major air battle developed over Dordrecht when six Supermarine Spitfires and six Boulton Paul Defiants encountered a formation of Junkers Ju 87 Stukas escorted by two squadrons of Messerschmitt Bf 109 fighters. The engagement was fierce and gradually drifted southward as the British aircraft divided into two separate groups. The British lost five Defiants, while German losses amounted to two Bf 109s and four Ju 87s. All these losses were confirmed. Wreckage from the combat was scattered across a wide area between Papendrecht and western North Brabant.
At approximately 0900 hours, Morane-Saulnier MS.406 fighters of Groupe de Chasse III/3, providing cover for French forces near Bergen op Zoom, encountered Bf 109Es of 1./JG 26. During one of the ensuing dogfights, a Morane and a Messerschmitt collided in mid-air over Hoeven, near Roosendaal. The French formation commander, Captaine Trouillard, was killed instantly, as was his opponent, Unteroffizier Speck. Shortly afterwards, Trouillard's wingman shot down another German fighter, which also crashed near Hoeven.
Only minutes earlier, fighters of GC III/1 had clashed with aircraft of JG 26 near Roosendaal. During that engagement, one Morane MS.406 was shot down north of the town, resulting in the death of the French airman, Flight Sergeant Pralon.
Elsewhere in western North Brabant, two Heinkel He 111 bombers of 5./KG 4 were shot down by French Curtiss Hawk 75 fighters at around 0900 hours. The victory came at a price, however, as two Hawks were probably lost to Bf 109s of 8./JG 3. None of the German bomber crewmen were killed, although several were wounded before being taken prisoner. The fate of the French pilots remains unknown.
Additional aerial losses occurred throughout the day. In the early evening, at approximately 1845 hours, a French Curtiss Hawk 75 fighter was shot down near Hulst. Earlier, around 1600 hours, a Potez 63.11 reconnaissance aircraft had been brought down near Oirschot. At approximately 1800 hours, a German Bf 109E crashed near Numansdorp following a brief air combat, while a twin-engine Ju 88 came down in flames near Roosendaal, the cause of which remains unclear.
British Blenheim Mk I aircraft were also reported pursuing a number of Bf 110s off the coast of Walcheren, although few details of this encounter have survived.
Taken together, these incidents illustrate the intensity of the air war over Zeeland and western North Brabant on 13 May. Although large-scale ground operations dominated strategic planning, the skies above the region remained the scene of continuous and often fierce aerial combat, involving aircraft from all major combatants