The Alblasserwaard was - like the Island of Dordrecht and Ysselmonde - in fact an island too. It was encircled by water-ways and bridges had to unlock the island. The Alblasserwaard lay north of the Island of Dordrecht and east of the island of Ysselmonde. It had hardly any military occupation to start with. The entire west side was unoccupied with the only exception of some semi-military air-watches.
In 1939 the large traffic bridge [400 meter long] at Alblasserdam - over the Noord river to the village of Hendik Ido Ambacht (island of Ysselmonde) - had been opened. It was an essential link in the newly constructed highway to Rotterdam, designated as the A15. The highway bit that lay on the Alblasserwaard side had been constructed in the years before. It was the intention that it would run to the south of Rotterdam, the harbour area. That last stage had not been delivered yet, but was still under construction. The bridge had been delivered though and used since November 1939.
The opening of the bridge had been celibrated in a very modest fashion, although normally these kinds of events saw massive press attention. It had been opened in November 1939, a time when newspapers had other focusses in those dark days of the first serious invasion rumours. This modest attention in the newspapers may well have facilitated the lacking knowledge of German intelligence services of the very existance of the bridge, although strong indications tell that it was merely a flaw in the bureacratic process of the Abwehr causing the bridge to remain unidentified on German staff maps.
The fact that Generalleutnant Kurt Student proved to be uninformed of the existance of the bridge is peculiar. The entire airlanding arena had been extensively photographed by Luftwaffe spy planes in particularly the first few months of the year 1940. Many high altitude flights had been registred, also by the RAF intelligence who had been able to trace many German flights over the western area of the Netherland. These spy flights were mainly performed by a special Luftwaffe unit that directly reported to the Abwehr. It may well have been the case that the Abwehr did in fact record the bridge over the Noord, but considered it not valuable enough to the airlanding operation and thus failed to pass the information on to the Luftwaffe HQ. More likely it was a flaw in the transfer of Abwehr - Luftflotte 2 transcripts of the reconnaissance results though.
Student himself blamed the Dutch, with a dot of irony that is! In his memoirs he stated that since the Dutch maps didn't show the existance of the bridge, the German battle maps had not copied it either. That in itself does make some sense, but Student of all people should also have valued accurate up-to-date information and that was usually gathered by active intelligence in particular. Anyway, the Germans remained oblivious about the bridge existance and as a consequence only two small taskforces had been scheduled to be sent to the northeastern sector of the Island Ysselmonde. They had to guard the westbank of the Noord against Dutch crossing attempts. Since no permanent Dutch troops were present on the other side, the taskforces had been kept small and amongst the last to be sent out. In other words - the northeastern perimeter had a very low priority.
The Light Division
In the early hours of the 10th - after the Dutch GHQ had received the shocking news of the lost bridge at Gennep and the armoured train that had penetrated the Peel-Raamline - the Light Division received orders  to immediately evacuate the province Brabant and redeploy at the Merwede front [around the city of Gorinchem]. Still during this evacuation process the commander of the division - Colonel Van der Bijl - received revised orders: 'move the division to Ysselmonde by making use of the traffic bridge at Alblasserdam. After crossing the bridge the division is ordered to prepare itself for action against the German troops at Waalhaven.' It was imperative that the airfield was retaken from the Germans.
The Light Division [hereinafter called LD] was the most mobile large unit in the Dutch army in those days. It comprised two infantry regiments [on bicycles] and one regiment of (motorbike)hussars. A second regiment motorbike hussars had been detached to The Hague and Wassenaar. Furthermore it had sixteen motorised guns [towed 7,5 cm field guns] and a strong AT-gun force [28 off 4,7 cm Böhler guns]. The two squadrons of wheeled AFV's [24 modern Landsverk M.36 and M.38 c/w a main gun of 3,7 cm, and two additional command cars M.38] had been detached from the division as well as two batteries of motorized infantry guns. One squadron of AFV's had been divided over the AFB's Ypenburg and Schiphol, the other squadron had been attached to the hussar squadrons that operated in front of the Grebbeline. The motorised light field gun detachment [towed 5,7 cm field guns] and the last regiment (motorbike) hussars had been left in Brabant when the LD started their displacement; the hussars would later rejoin the division. All together the LD had not a full divisional strength of 10,000 men. It would eventually be able to bring almost 7,000 men to the Alblasserwaard.
The LD arrives
During the afternoon the division commander [Colonel Van der Bijl] received the new instruction that the division had been ordered to counter attack the German occupation at Waalhaven AFB after it had send one infantry battalion to Dordrecht. At 1700 hrs new contact had been established with the Commander Fortress Holland. During that telecon a more genuine intelligence package was received. The Colonel was informed that the divsion had to be in position east of Waalhaven at a time that would make it possible to start the attack at 0200 hrs [11 May], the time that was advised by the RAF as the estimated time that a planned large scale RAF raid on Waalhaven would have ended.
Apparently the Colonel had not been informed that the bridges at Dordrecht and Barendrecht had been occupied by German troops. That conclusion can be deducted from the operational plan that the Colonel designed. He instructed two forces to be formed. One that would move south into the direction of Barendrecht [where meanwhile parts of a German battalion had been positioned] and one that would go north to Bolnes (along the Maas). The southern force had to send one battalion to Dordrecht via Zwijndrecht (!) after it had crossed the Noord. That very detail is a clear indication that the Colonel had no knowledge of the German positions, for otherwise he would have sent the battalion over at Papendrecht (directly opposite of Dordrecht), because the Zwijndrecht bridge was after all occupied by the Germans. Also, he apparently knew nothing about the German positions around Barendrecht.
After the two taskforces would have reached the line Barendrecht - Bolnes, they would simultaneously move forward and take positions on the eastern and southern angle of Waalhaven AFB. The whole plan was quite shallow. The Colonel had no knowledge of the dislocation of the opponent, knew little of its strength. The troops were unaware of the challenge of the totally flat and open polder that lay ahead of them. But most importantly, the plan was very ambitious given the fact that most of the division was still in the process of even getting to Alblasserdam and surroundings, but yet had to be ready to assault Waalhaven at 0200 hrs!
At 2100 the first units [of the 2nd Regiment Bike Infantry] of the division had reached the region of Alblasserdam. The majority of the second part of the division was still way behind making its way westwards.
Meanwhile the Colonel had made contact with the bridge operator. The bridge deck had been lifted earlier that day, after a German airborne landing had been witnessed on the other side. During the late afternoon a car full of German soldiers had arrived on the Ysselmonde end. The Germans had driven up to the opened deck and shouted to the other side - where the operator building was situated - that the operator had to lower the bridge. He had refused upon which the Germans had turned and left. The Colonel praised the operator but at the same time feared that the Germans would be ready for his men to cross the bridge and the Colonel didn't fancy a night fight.
The Colonel's perception - or rather his lack of tactical assessment and initiative - would play a possibly decisive role in the (success of the) entire German operation as well as the (lack of) effectiveness of the Dutch counter measures still ahead.
The German side
Generalleutnant Student had been genuinely shocked when a recce party had returned with the news of the whereabouts of a major bridge that did not appear on his battle map. More worrying was the assessment that Dutch forces had been spotted on the opposite end, for at that time he could not think of what Dutch outfit that could be.
It had forced Student to slightly alter plans. In the late evening he directed two companies of II./IR.16 to quick-march to Alblasserdam and take a battery of 7,5 cm mountain howitzers along with them. The battalion had to prevent any Dutch crossing. He promised their commander that he would appeal on the Luftwaffe Gruppe Putzier to see to air support in the early morning. As such a German force of about 300 men was about to counter the Dutch offensive plans even before they had started to unfold.
The German occupation at the bridge had been very light until late that night. After the first discovery of the bridge in the early afternoon, the commander of IR.16 had considered it not more than a nuisance that the bridge had been overlooked. Since no Dutch forces were expected in that area, he had only sent one platoon with a single AT gun to the bridge to guard it. When General Student received news - late in the evening - that large Dutch army units were in arrival at Alblasserdam, he grew not only extremely worried but wondered where the hell these Dutch forces came from ...
His counterpart operated quite the opposite way. When the Dutch Colonel had realised that at least some German troops were already occupying the westbank, he had ordered the first arriving battalion of the LD to cross the Merwede at Papendrecht [to Dordrecht] in stead of using the bulk of this unit for an immediate crossing attempt. The Colonel had sealed the fate of his battle plan with that conservative and unwise decision. He had decided to await the arrival of his other units to undertake the offensive and he preferred to undertake it by daylight - in other words - at the 11th. He did not even consider sending a recon party to the other side to probe the enemy's strength! A tactical blunder of magnitude that played right into the German cards! It also meant that the plan to follow up on the RAF raid on Waalhaven was left. It was a typical example of the Allied incapacity to make the right operational and tactical decisions when opportunities occured on the battlefield. The French, Belgian, Dutch and partially British field commanders of May and June 1940 all seemed to miss this operational boldness that many German field commanders possessed, and that basically represented the most significant difference between the two sides in that period of time.
At about 0400 hours the companies of the 2nd Battalion of IR.16 arrived at the Noord, together with a battery of mountain-artillery guns of 7,5 cm and some AT guns. Two German platoons manned the bridge area, another two platoons were sent to Ridderkerk. The Dutch window of opportunity had been closed.
The total lack of initiative and poor tactical thinking of a division commander had slammed the door on possibly the best opportunity the Dutch had to seriously jeopardize the success of the German airlanding operation. It was a mixture of poor and inadequate information from the staff of the Fortress Holland Command and a total lack of initiative on divisional level. But yet, the around 3,000 men Dutch troops that would mass along the Noord in the morning of the 11th would still have the opportunity to cross the Noord, albeit under much more enemy pressure than should have been necessary ...