The province of Zeeland occupied no prominent place in Dutch strategic defence planning. Apart from its seaports - especially Vlissingen (in English = Flushing) - and its strategic significance in relation to Antwerp, Zeeland was regarded by the Dutch General Staff as little more than a secondary defensive sector.
Nevertheless, Zeeland was considered to possess some strategic importance for two principal reasons. The first was the defence of the island of Walcheren, regarded as the administrative and civil centre of the province, containing both the provincial capital Middelburg and the important harbour of Flushing.
The second reason was political in nature. Zeeuws-Vlaanderen, the southernmost part of Zeeland, had been the subject of Belgian territorial claims during the negotiations surrounding the Treaty of Versailles in 1919. Belgium had sought annexation of this Dutch territory because of its strategic position controlling access to the Scheldt and the harbour of Antwerp. Although the British and Americans rejected the Belgian claim in 1919, the Dutch military nevertheless considered it prudent to station troops in Zeeuws-Vlaanderen in order to deter any potential Belgian action there and thereby prevent the revival of Belgian territorial ambitions and claims. This situation illustrates the extent to which Dutch–Belgian relations remained strained on the eve of the German invasion in 1940.
The only two islands in Zeeland that contained defensive forces of any significance were Walcheren and Zuid-Beveland, of which the latter was connected to the mainland of Noord-Brabant by bridges and causeways. The other islands were either entirely isolated or connected only by long bridges, and their small garrison forces were far too weak to resist any invasion of serious scale. In addition to these limited army formations, Zeeland possessed a number of coastal defence positions, consisting of navy and coastal batteries located at strategic points throughout the province. These positions were intended primarily to counter potential maritime operations by an enemy force.
Two principal defensive lines had been prepared in Zeeland, both situated on the island of Zuid-Beveland. The main defensive position, known as the Zanddijkstelling (hereafter the Zanddijk Line), ran through the centre of the island and partly followed an intersecting canal. In front of it lay a thinner forward defensive position, the Bathstelling (hereafter the Bath Line). Both lines were located on the eastern side of the peninsula formed by the connected islands of Zuid-Beveland in the east and Walcheren in the west. As noted above, these two islands - regarded as the principal islands of Zeeland - were the only ones with reliable connections to the Dutch mainland.
The southernmost part of Zeeland, Zeeuws-Vlaanderen, was also connected to the mainland - indeed, it formed part of the continental mainland itself - but it was separated from the rest of the Netherlands by Belgian territory. Consequently, communication with the remainder of Zeeland depended largely on the intensive ferry services operating between the port of Flushing and the Zeeuws-Vlaanderen port of Breskens.
Apart from the two defensive lines discussed above, Zeeland contained few prepared land defences. The province was, however, relatively well fortified along its coastline, as was already briefly addressed hereabove. A considerable number of coastal batteries and fortifications were present and manned, while the harbour of Flushing (Vlissingen) was also protected by defensive works. Six coastal artillery batteries, constructed in earlier years, were operational in May 1940. Four of these were located along the coast of Walcheren: at Dishoek (equipped with three 15 cm guns), at Westkapelle (with three 12 cm guns), at Oostkapelle (with three 15 cm guns) and at the harbour of Flushing, which was defended by three 7.5 cm guns. The fifth battery was situated on the northern island of Schouwen and was likewise armed with three 7.5 cm guns. The sixth and final battery stood at Nieuwe Sluis, on the western coast of Zeeuws-Vlaanderen, and also consisted of three 7.5 cm guns.
In terms of Dutch military strength, Zeeland was regarded as a secondary sector of limited importance. Command of the province had been entrusted to a naval officer, Rear Admiral (lower half) Van der Stad. Owing to Zeeland’s extensive coastline, the presence of an important naval base, and the peacetime responsibility of maintaining Dutch neutrality in the surrounding waters, the government had appointed a naval commander as territorial commander. All other territorial commanders in the Netherlands were army officers. Only the positions of Amsterdam, Hook of Holland, Ymuiden, and Fortress Den Helder (the main navy harbour) likewise had naval commanders, although these were fortified naval positions rather than territorial commands.
The Territorial Commander of Zeeland had approximately 7,500 land-based troops under his command. The core of this force consisted of two infantry regiments, the 38th and 40th Infantry Regiments. Both belonged to the so-called “high-numbered” regiments and were composed largely of older reservists; unlike the first twenty-four “low-numbered” regiments, they possessed only limited supporting units.
In addition, a border infantry battalion (14 GB), two reserve border infantry companies (14 GC and 38 GC), and a company of protection troops also fell under his authority. A small naval auxiliary detachment, including several dozen well trained marines, was stationed in the harbour of Flushing, although this force contributed little in terms of actual combat capability.
Van der Stad also commanded an incomplete artillery regiment. This regiment included a full battalion equipped with obsolete artillery pieces - twelve 8-staal (Krupp 1880 class, 8.4 cm) field guns. Moreover, the 1st Battalion of this unit had already been dispatched to the southern front near Dordrecht. What remained in Zeeland consisted of only twelve modern 7-veld field guns (Krupp 1904 class, 7.5 cm), two medium 10 lang 30 field guns (Krupp 1912 class, 10.5 cm), and the twelve obsolete field guns of 8-staal. In practice, therefore, Zeeland possessed only a single battalion of modern artillery. Obviously, naval gun support could add to this modest land based fire power.
Altogether, Rear Admiral Van der Stad commanded no more than half a division worth of forces, supported by only a very modest number of heavier weapons. The overall quality and combat readiness of these troops ranged from mediocre to poor. The bulk of the defensive force was concentrated on the islands of Walcheren and Zuid-Beveland, where approximately six infantry and naval battalions, together with the incomplete artillery regiment, were deployed. A further force equivalent to roughly two battalions was dispersed across positions on Zeeuws-Vlaanderen and Schouwen-Duiveland.
Zeeland possessed two air bases on its territory. Haamstede Air Base, which served as a secondary flight training school, was located near the coast on Schouwen-Duiveland, while Souburg Air Base, an elementary flight training school, lay just north of Flushing on Walcheren. Both airfields housed only unarmed training aircraft, although this situation would change at Haamstede during the first day of the war.
At Veere, the Royal Netherlands Navy maintained a small base for a squadron of six older seaplanes.
Anti-aircraft defences in Zeeland were limited. Heavy anti-aircraft artillery was available only at the two airfields - three 7.5 cm Vickers guns at Vlissingen and three 4 cm Bofors guns at Haamstede - together with a battery at the Zanddijk Line equipped with three obsolete Krupp 7.5 cm AA guns, a Dutch own adaption. The harbour of Flushing was defended by two platoons of heavy anti-aircraft machine guns. It was assumed that the naval vessels present at the country’s second-largest naval facility would provide sufficient additional anti-aircraft fire against enemy air raids. At Veere, northwest of Zuid-Beveland and the location of the naval seaplane base, a third heavy AA machine-gun platoon was stationed. The commander of the naval base there also had three naval 20 mm Hispano-Suiza guns available for anti-aircraft duties.
The port of Flushing itself represented both an important naval base and a harbour of considerable economic significance, with extensive docking and mooring facilities. The naval and civilian shipyard De Schelde was of particular importance. As one of the principal shipbuilders in the Netherlands, it was regarded by the Dutch authorities as a prime target for enemy air attacks. In May 1940, the yard was constructing four new naval vessels, three of which - a large gunboat and two highly modern submarines - were evacuated in time to England, where they would later serve with distinction in the Royal Navy under Dutch crews.
Several major Dutch naval vessels were anchored off Flushing on 10 May, including the light cruiser Hr.Ms. Sumatra and the heavily armed gunboats Hr.Ms. Johan Maurits van Nassau and Hr.Ms. Flores. The latter vessels, equipped with 15 cm main batteries, had been designated to support the defenders of the Bath Line, who otherwise lacked substantial land-based artillery support. Both Flores and Sumatra would serve a role during the D-Day landings in June 1944.
In addition, a considerable number of smaller naval units were stationed at Flushing at the time of the German invasion. These included fifteen auxiliary naval vessels — mostly armed civilian tugs and pilot boats fitted with either 3.7 cm or 5 cm deck guns — two minelayers armed with three 7.5 cm guns each, two auxiliary minesweepers, and two obsolete shallow-water gunboats. A militarised cargo vessel and a hospital ship completed the naval contingent in Flushing. Alongside the naval presence, the harbour also contained numerous small and medium-sized civilian vessels, including several large and modern ferry ships.