Northern provinces - Introduction
Before we address the events in the northern provinces, a brief introduction should be given of some events that preceded to the forming of the Dutch battle plan for the northeast. After that we shall discuss the specifics of the northern defences on the eve of battle.
The three most north(east)ern provinces of the Netherlands [Friesland, Groningen, Drente] were - strategically - the most insignificant Dutch territory on the main-land. The main Dutch strategy was based on the firm defence of the western part of the country [see: Dutch army strategy] and the outer-defences [delaying defences] had all been concentrated along major rivers and canals [dislocation of the troops was emphasised to the Fortress Holland and the main defence- and delaying-lines] that lay in front of the main-defences.
To the north of the sector Zwolle / Kampen such geotechnical barriers were not available and moreover their were no main-defences lines east of this sector. The vast IJsselmeer was a main-defence in itself but only passively so. It is clear that the northern provinces lacked any strategically significant position or landmark.
The only liability that the north provided to the main strategic plan was the recently constructed "Afsluitdijk" [hereinafter "Afsluitdike"]. This dike [in fact a dam] had been constructed to create a sea-barrier for the IJsselmeer [Yssellake]. Due to the dam-construction the lake had lost the tidal water-level differences [as well as the salty water content] and furthermore a quick land-connection between the northwest and northeast had been established. Prior to its construction a 30 kilometres wide water-gap between the provinces Friesland and North-Holland had existed. That gap had always been considered wide enough to concentrate all (northern) defences on the west-shore of the Yssellake. Up to the point that the Afsluitdike had been constructed , the north-eastern provinces had not been incorporated in any [modern] defence plan.
When in the late years of the twenties it became clear that the civil authorities were authorised by the Government to construct the dam, the Ministry of War protested. They lacked the funding to construct ample defensive fortifications on the extremities of the dam and demanded that such funding would be raised by the civil authorities. This concession was granted and consequently a considerable amount of money was allocated for the construction of two major fortified complexes at both the eastern [Kornwerderzand] and western [Den Oever] extremities of the dam. After the dam was delivered and opened to the public, the two formidable fortresses had been transferred to the Ministry of War. It would proof to be the most modern and most effective fortification the Dutch army would posses in May 1940.
The side-effect of the construction of the dike would however be that the Dutch military were by then forced to form some sort of defence in the north in order to prevent an enemy to be able simply moving its troops and vehicles through the three northern provinces unchallenged and as such opposing the fortresses within half a day or so after an invasion. A scenario like that would be a highly undesirable one. Also, some sort of plan was to be developed to prevent the Germans of simply entering the many small harbours on the east shore of the Yssellake, requisitioning available shipping space there and cross the Yssellake. The military authorities required some window to be able to destroy facilities and evacuate / destroy shipping when an invasion had become a fact. As such a true but modest strategic plan was developed for the three subject provinces.
The defence plan
The whole defence plan swivelled around two major objectives: gain adequate time to take accurate precautions at the east-shore harbours and organise the defences around the Afsluitdike. All planned actions and precautions in the eastern sector of the provinces Groningen and Drente were designed to achieve these two objectives.
As such a couple of thin defences were constructed [or formed]. A very thin defensive screen [forward positions] was organised along the border with Germany, designated as the O-line. Behind this forward position a slightly reinforced delaying defence-line [Q-line] was designed, which ran from the Eems [water in the northeast] to Hoogeveen, where it curved towards the west towards the Ysselmeer [F-line]. The O and Q lines were close to the German border. In Friesland - the most western province - there was only one defence-line projected. That was an arc-shape defence a few clicks east of the landhead in front of the Afsluitdike. It was called the Wonsline and, although insignificant in comparison to many other defence-lines in the country, it was the most significant prepared defence system in the entire north.
When the Germans would eventually have taken the Wonsline out, they would be halted by the formidable fortress Kornwerderzand. This fortress was situated about 4 km offshore on the large dam. The fortress had been constructed at the sluice complex that had provided for some space were a rather extensive fortification system could have been built.
The fortress at the Friesland end of the dam was called Fortress Kornwerderzand, The narrow causeway between the fortress and the main-land was only some 40 m wide and totally flat, without any obstruction whatsoever: a perfect firing window for the fortress-gunnery and machineguns.
The fortress itself comprised no less than 17 casemates. Most of these were of the heaviest type available in May 1940. They were designed to be able to withstand continous indirect 21 cm projectile impact as well as the ocassional 28 cm indirect rounds. The roofs of the main casemates had been constructed of 300 cm thick reinforced concrete. The walls were 150-200 cm thick. The armament comprised light machineguns, heavy machineguns  and some  5 cm anti-tank guns. Spare machineguns were available; ammunition was available in huge quantities.
The weapons were divided over two lines of casemates; the majority was aimed to the east, the rest to the west. some weapon points could also cover the sea- and lake-sides against amphibious landings. A number of search-light positions had been constructed in order to be able to light the dike during night hours. Furthermore living quarters and water purification facilities had been incorporated in the complex that could shelter 230 men personnel. Telecommunication lines with the east-coast and west-coast had been well prepared. Food, water and other stocks were suitable for one month prolonged action.
Steel barriers could be fixed in the causeway-road, mine-fields had been prepared and a large stock of landmines was available for use after hostilities had broken out. The only thing that was not available was AAA. A similar complex was built at the western side of the dike at Den Oever.
In the middle of the dike, around another sluice complex, a small unit was stationed with some machineguns to prevent a German landing in the rear of the fortresses. They lacked any fortifications whatsoever.
The O, Q, F and Wonsline were manned by a very modest force. When General Winkelman took over the General Command of the Dutch army in February 1940, he had even moved some more troops away from the northern provinces.
The first three lines and the forward positions along the border had the basic task to slow down the enemy and blow up as many bridges as possible. One should be aware that well over 200 bridges were constructed over the various small rivers and canals in these provinces! And not all of these had been prepared for destruction.
Artillery was not available at all; it was too scarce to waste it at a subsidiary front. Some obsolete 57 mm and 84 mm infantry guns were available, as well as the occasional modern anti-tank gun. The Kornwerderzand complex could be assisted by naval guns from surface units in the Waddenzee or the few gun boats that patrolled the IJsselmeer.
In total a mere 4,000 men had to defend the entire north. A little more than the equivalent of 5 battalions. In order to be able to compare this very modest force to the requirements of those days: in the main defence lines of the Dutch army the standard front-width of one battalion had been determined to be 1 km. In other words, almost one man per metre. The width of the front of the Q-line alone was over 25 kilometres. Bearing in mind that four lines had to be defended by 4,000 men, one could easily predict the odds ...
The navy had formed a very modest IJsselmeer flotilla. The designation 'flotilla' was a eufemism. It only contained obsolete gun boats and some lightly armed sloops. The smallest navy unit was the Z-3 gunboat [1915, 263 tonnes, 2 x 7,5 cm guns]. The biggest unit was the gun boat Hr Ms Friso [1911, 542 tonnes, 4 x 10,5 cm guns]. At 10 May the sistership of the Hr Ms Friso, the Hr Ms Brinio, was also shifted to the IJsselmeer flotilla.
The bigger units were supposed to patrol the eastern shore of the IJsselmeer in order to prevent the Germans of crossing the large lake to the west. The east shore had a total length of over 120 km from Apeldoorn to Kornwerderzand. The west and southwestern shores were guarded by small sloops that had only one or two heavy machineguns on board. The distance to cover from Den Oever to Amsterdam alone was 80 km. The leg from Amsterdam to Apeldoorn another 30 clicks.
The opposing force
The German offensive plan was quite down to earth in regard to its first stage: reach the shores of the Ysselmeer. The second stage - penetration of the Fortress Holland via the northwest - was very ambitious, or one could say quite unrealistic.
The German forces were instructed to take the northern provinces, occupy the harbours and requisition shipping room for a landing on the west-shore of the Ysselmeer and - last but not least - take the defences at the Afsluitdijk. After this the division had to take the north-western land-head, form a screen against Fortress Den Helder and proceed southwards into the direction of Fortress Holland.
This very ambitious directive had to be executed by the reinforced [last traditional] German Cavalry Division [1st Kavallerie Division, Generalmajor Feldt - later the 24th Panzer Division]. The Division - part of the 18th Army - comprised four cavalry regiments, a bike-infantry battalion, a light artillery regiment, an anti-tank company, a pioneer battalion, a signals battalion and some miscellaneous smaller units.
The division had quite some heavier firepower at its disposal: 33 anti-tank guns, 37 mortars of 81 mm, 52 guns of 75 mm, 8 guns of 2 cm FLAK, 8 guns of 88 mm FLAK and 18 armoured cars.
An armoured train [Zug 6] was assigned, which was equipped with a 75 mm gun, two 37 mm guns and a Vierling [quadruple] 2 cm FLAK machinegun. The train was supposed to ride straight through all Dutch defences and reach the Afsluitdike.
Also the Sonder Kommando Stein [Korvettenkapitän - rank equal to navy Lieutenant-Commander - W. Stein] was incorporated in the division structure. This Kriegsmarine commando was especially trained to organise the shipping-room once the harbours had been sieged. subsequently it would coordinate the Ysselmeer crossing.
Altogether a force of about 15,000 men, reinforcements included.
Contrary to the stakes the ambition that the strategic plan breathed out was more than ambitious and bore the clear signature of underestimating the defences. Obviously the thin screen of outer defences couldn't worry the Germans a bit. But the natural barriers formed by the Ysselmeer and the narrow dam, seemed to be underestimated. The cavalry troops were not at all laid-out for amphibious operations and the vast Ysselmeer - a grave to many fisher men and traders - had a treacherous swell. The peculiar choppy swell required good seamanship. Simply shipping these land soldiers across at least 20 km of inland sea was quite an operation and it was hugely underestimated by the Germans. Especially if one bears in mind that some navy units would be met and although the Luftwaffe would probably show some teeth, the vessels that could be used for an amphibious operation would be sunk in no time by the larger surface units.
On the other hand the German command didn't really care. The operations in the north were of the lowest priority in the entire Fall Gelb spectrum. The failure or success of the 1.KD wouldn't really matter for the end result and the prevailing thought was that even the smallest German presence in the north of Holland would prevent Allied troops from even considering any amphibious landing over there. Any result would be nice for the overall scoring board, but be insignificant on the larger scale. Against that wall paper the events should be measured.