In August 1911, British soldier General Henry Wilson penned a letter on how England should prepare for a future war involving Germany:
What should be our foreign policy, speaking of course from a military point of view?
…If we examine the map, we can see the value to us and France if Belgium is actively hostile to Germany. But as far as my knowledge goes Belgium will remain passive and neutral if she possibly can even if, and when, German armies over run all her country south of the Meuse and Sambre. She will remain passive and neutral unless she is convinced that we are going to join France and are determined to fight this war out to a victorious finish.
If Belgium believed this, she would join with us. And for this reason: she hates the idea of being absorbed into the German Empire and she fears, and with good reason, that even if she remains neutral she will as a matter of fact be swallowed up by her big neighbour after the war is over, if Germany is victorious. On the other hand she knows that neither England nor France have any designs on her independence and she would incline to them if she was persuaded that they had determined on joint action.
My opinion therefore is that, for the single and specific case of an unwarranted attack by Germany on France or an attempt by Germany to seize or absorb Belgium, England and France should have an offensive and defensive alliance and in this Belgium would join. Whether Holland could be induced to join I am not sure, nor do I much care. Denmark ought to be brought into it and I take it for granted that Russia is already there.
A Belgium hostile to Germany would mean that the line of the Meuse was secure, that the fortresses of Namur and Liège and the work at Huy were impregnable. It would mean an open and friendly country for us to operate in, it would therefore mean a constant and ever increasing menace to the German right flank and the German line of communication; and most important of all, it would mean that the superiority in German numbers could not be brought into play. A hostile Denmark might very well mean an appreciable reduction of German forces on the French frontier…
The difference that such a state of affairs would make on our strategy would be incalculable and, again writing as a soldier… I would press with all the weight I possess for a (circled) offensive and defensive alliance between ourselves, France, Belgium and, if possible, Denmark.