The Island of Tholen was effectively a naturally detached fragment of the province of North Brabant, separated from the mainland by the 'Eendracht', a shallow and muddy tidal waterway. It lay northwest of Bergen op Zoom and north of the island of Zuid-Beveland, from which it was separated by the broad waters of the Eastern Scheldt (Oosterschelde).
This geographical isolation was one of the reasons why Tholen - otherwise a remote and strategically unremarkable corner of the country - received a modest military garrison. Had the island been left undefended, General Durand's concerns about a German crossing of the Oosterschelde in assault boats would have been more justified.
The main city on the Island Tholen was the small town Tholen, which also harboured the only (artificial) main-land connection with Noord-Brabant. On the east-side of the town Tholen an ancient dfence bastion had been reinstated [like at the Grebbeberg], that defended both sides of the road leading towards the (only) bridge. On the westbank of the Eendracht a thin front was formed along the waterway. At three locations permanent positions had been prepared, whilst the balance of the west bank was guarded by patrols.
The entire occupation of the island - a little more than two companies of 1st Battalion of 38.RI - was concentrated along the Eendracht. The companies were supported by two 5,7 cm infantry guns, two 8 cm mortars and twelve heavy machineguns. The total occupation was no more than about 450 men.
At the bastion on the eastbank three platoons of infantry and two heavy machineguns - about 100 men altogether - defended the road. The bastion itself was surrounded by a stretched inundation that covered two-third of the eastbank of the Eendracht. The town - west of the bastion - was occupied by a platoon of infantry close to the bridge, two twin gun sections of heavy machineguns along the Eendracht and the two mortars, which could give fire support to the bastion. Another platoon of infantry and two heavy machineguns were stationed north of the town as a reserve. The battalion HQ and supporting units were situated in the small town.
The northern sector was - again on the westbank - defended by two sections of heavy machineguns and the two 5,7 cm guns joint, by three platoons of infantry [of the 1st Company]. The fourth platoon of the company defended - on the westbank - a narrow point in the Eendracht just north of the inundation.
During the previous days the usual picture was seen. Plenty of patrolling action as a consequence of yet again many airborne warnings. On the 12th and 13th about 200 men Dutch troops from the eastern Brabant front had reached Tholen, and had been sent to the unoccupied western part of the island. These troops were later shuttled over to Walcheren by boat. At the 13th the bridge over the Eendracht had been blown up. From then on the platoons on the bastion were isolated and had to be supplied by means of small boats.
The principal settlement on the Island of Tholen was the small town of Tholen itself, which also contained the island’s only fixed connection to the mainland of North Brabant. East of the town, an old defensive bastion - much like those reactivated at the Grebbeberg - had been restored and slightly fortified to guard the road leading to the island’s sole bridge crossing.
Along the western bank of the Eendracht, a thin defensive screen had been established. Permanent positions had been prepared at three key locations, while the remainder of the waterfront was monitored by regular patrols.
The island’s entire garrison, consisting of little more than two companies from the 1st Battalion of the 38th Infantry Regiment, was concentrated along the Eendracht. These troops were supported by two Krupp 57 mm infantry guns, two modern 81 mm mortars, and twelve heavy machine guns. The companies each had 8 light machine guns type Lewis, a 6.5 mm version of the orginal British weapon. In total, the garrison numbered no more than approximately 450 men.
The bastion on the eastern bank was defended by three infantry platoons and two heavy machine guns, amounting to roughly one hundred men. The position was protected by an extensive inundation that covered approximately two-thirds of the eastern bank of the Eendracht.
The town itself, situated west of the bastion, was defended by an infantry platoon positioned near the bridge, two twin heavy-machine-gun sections covering the Eendracht, and the two mortars, which were capable of providing indirect fire support to the bastion. A further infantry platoon and two heavy machine guns were stationed north of the town as a local reserve. The battalion headquarters and supporting units were also located within the town.
The northern sector, likewise situated along the western bank, was defended by three infantry platoons of the 1st Company, supported by two sections of heavy machine guns and the two infantry guns. The company’s fourth platoon occupied a narrow stretch of the Eendracht just north of the inundated area.
During the preceding days, the now-familiar pattern had repeated itself. Numerous reports of enemy airborne landings generated a constant stream of patrol activity across the island. On 12 and 13 May, approximately 200 Dutch soldiers retreating from the eastern North Brabant front reached Tholen. These troops were initially sent to the previously undefended western part of the island before later being transported by boat to Walcheren.
On 13 May, the bridge across the Eendracht was demolished. From that moment onward, the platoons occupying the bastion on the eastern bank became effectively isolated and could only be supplied by means of small boats crossing the waterway..
At the bastion, the defenders spotted a German patrol approaching their position at approximately 1700 hours on 15 May. A brief burst of machine-gun fire was sufficient to drive the patrol back. Shortly thereafter, two German emissaries appeared, advancing cautiously towards the Dutch roadblock in front of the bastion while prominently displaying a large white flag. A Dutch officer and a German-speaking sergeant were sent forward to meet them.
The German representatives demanded the immediate surrender of what they referred to as "Fortress Tholen". They argued that, since the Dutch Army had already capitulated, any refusal would result in a heavy bombardment of the position.
The ultimatum was relayed to the Dutch battalion commander, who promptly drafted a written reply. He pointed out that Tholen formed part of the province of Zeeland, which had been explicitly excluded from the armistice. Consequently, the island would continue to resist. The response further stated that Dutch forces would open fire fifteen minutes after the Germans had received the letter. The emissaries wasted no time and quickly returned to their own lines.
At 1800 hours, German field artillery and mortars positioned along the approach road commenced a bombardment. Most of the shells fell on the eastern outskirts of the town rather than on the bastion itself, which the Germans may not yet have identified accurately, as the roadblock was situated well in front of the actual defensive position. Apart from a direct hit on a gas storage tank, the shelling caused little damage.
Shortly after the bombardment ceased, German infantry advanced on both sides of the road. The Dutch defenders held their fire until the attackers had approached the roadblock. Then the mortars and machine guns opened up simultaneously.
The effect was felt. Numerous German soldiers were killed or wounded, while others desperately jumped into the flooded areas surrounding the position in an attempt to escape the fire. Under mounting casualties, the attackers gradually withdrew while returning fire as best they could. German reports later recorded approximately twenty men killed or mission in action. Dutch losses amounted to just two men killed.
The engagement nevertheless convinced the Dutch battalion commander that the position could not be held indefinitely. The Germans now knew the location of the bastion, while the trenches and machine-gun positions consisted largely of improvised fieldworks offering limited protection against a determined bombardment. He therefore decided to evacuate the forward position during the night.
Late that evening and throughout the hours of darkness, the bastion was quietly abandoned. The troops, together with their machine guns and other equipment, were ferried across the Eendracht in small boats. Once on the western bank, they were assigned new positions along the waterway.
As night settled over the island, the Dutch defenders awaited the next German move. They possessed neither searchlights nor illuminating flares with which to light the darkness, and beyond the faint sounds of activity across the water, little could be seen. The men could do little more than watch, listen, and prepare themselves for what the coming day might bring...