Interesting theme.
It depends when the Germans invade. There several options as almost ocured in OTL;
1) In August as part of the West offensive, but this mean that the Dutch would only be confronted with first rate troops in the South, Provinces Limbourg and Brabant.
2) 1916 and 1918, this was a partial invasion with he aim of securing the Province Zeeland in order to give the Imperial Navy a better U-boat base.
Let asume you mean the first option 1914 as part of the large West offensive.
Despite the , somewhat, defalist attitude of General Snijder, comander of the Dutch armed forces the state of the Dutch army was for 1914 standards up to date and modern. Many people confuse the state of the Dutch army in 1914 with that of 1940. There were some short commings, like modern heavy artilery, but these were awkonledged and were planned to be solved.
The soldiers of the field army were equiped with a relative modern rifle. Were dressed in a modern, field gray uniform. ( the Frenc had to wear bright red trousers and kepies).
The Dutch mobilised their army as one of the first nations, it was fully mobilised and all units were on their positions when hostilities broke out.
The main objective of the field army was to deny and delay an invading army in order to win time to complete the inundations of the Hollandse Waterline and the Zuidwater line.
The Germans would use their first rate troops only in the South as part of their masive push South to France. Their right flank, the rest of the Dutch and Belgian army would be confronted with second, third or even fourth rate troops. (as in OTL 1940)
The initail consequences would be, after negotiating the destroyed bridges over the river Meuse in the Netherlands, a broader front for the German 1st and 2nd army. The fortress of Liege would be not so much an obstacle for the German advance and circumvailed Possible that this will have consequences later on the Sothern Front with the French and BEF.
The Belgian army would most likely keep contact with the Dutch army and would retreat North West in stead of South West keeping contact witht he French. Since the river Scheldt is now open to supplies and reinforcements to Antwerp it makes it more likely that the Belgian army retreat North West in order to secure the South bank of the river Scheldt.
This result in less presure to the German advance South but also threaten the German right flank even more, although I do not hink there will be significant reinfocements or support from Great Brittian or France entering Antwerp. As in OTL the Belgians were more or less left alone at this stage of the war, except the British naval troops. The BEF will be connecting with French troops as in OTL.
Never the less a connecting with Dutch and Belgian troops will threat the German right flank and a possible outbrake in Spetember as in OTL could be more damaging. It will not be a sustained offensive since the Dutch and Belgian army were not capable of large scale counter offensives.
The ring of fortres of Antwerp would probably be broken as in OTL since it was not supported by inundations. The Hollandse water line and part of the Zuid water line could be held. No doubt many of the forts of mentioned lines would be shot to rubble but the main defense were the inundations. In OTL the Belgians stopped the German advance in an Ad Hoc water line so a enginered and prepared water line must certainly stop a German advance. Given the fact that the Germans at this secondary front were not the first rate troops as at the main front.
I imagine that at the end of 1914 the front will be as follows:
Main front will be entierly in France, The part of the front West of Paris will be much more South. May be the Line Boulogne-Doulens-Alber-St Quintin.
In the North, the Belgian Army will defend a strip of Belgian soil North of Bruges and Genth. essentially defending Dutch Zeeuws Flanders. Posiible usinng the old 16 century Spanish and State lines, earth works and inundations. The Dutch would hold the line at Walcheren, the Sloedam. as in OTL 1945 German army.
The Hollandse water line will be held only at the city of Utrecht, were the inundations are the weakest the main point of fighting will remain.
Consequences:
City of Utrecht will be shot to pieces as OTL Ieper. Ieper will survive in this TL as many of other towns and cities in West Flanders and Pais de Calias contrary to OTL.
Bergen op Zoom will be heavily damaged if not destoryed as part of the defense of Antwerp. Dendermonde will be destroyed as in OTL during the defense of Antwerp. Antwerp will be much more damaged as in OTL since the city will be defended more longer since its port will be open.
Heavy damage to Bruges, Genth, Vlissingen, Middelburg ( Zeeland) due to long range artilery of both sides. OTL 1940 Middelburg was shot in flames by French artilery at the South bank of the river Scheldt. Possible this happen in this TL as well.
Heavy damage to towns and cities in the Netherlands as in OTL Belgium during the advance of German troops.
Occupied Netherlands will undergo the same burden of destruction, looting and cruelty as Belgium (OTL)
Due to an occupied or blocked Netherlands, Germany will be deprived years earlier of essential supplies to maintain the war of atrition.
There are less troops availabel for the main fronts and needed to occupy the Netherlands next to Belgium.
North front with its inundations is not suited for offensives, the risk of a break through from the Dutch/Belgians will be limited.
Possible Churchill and Fisher will come up with an offensive plan to invade the North of the Netherland and East Frisia in an attempd to conquer the naval base of the Hochsee flotte; Wilhelmshaven and the Jade.
As mentioned in earlier post, it would be require a masive effort to supply around 2 to 3 milion people in Vesting Holland. Despite that in 1914 most of the Provinces of South and North Holand are not that urbanised as totday, the framers can not produce enough food.Beside this most of Holland is pasture land only suitable for dairy farming.
The supply convoys would be a major target for U-boats, Destroyers or trigger any other Naval action. It might even cause a much larger and frequenter use of the capital ships of Great Brittian and Germany.
