David Maynard is absolutely correct in his reply.
In 1914 Britain was very conscious of the growing power of Germany, and feared having to fight Germany alone.
With the advent of steam ships, we could not afford to have a powerful army sitting where the Duke of Parma's had sat in 1588. Only hours notice would be given of any descent on ourshore.
We could not rely on the Protestant Wind anymore.
The Grand Fleet was not that much superior to the German High Seas Fleet, and in the right conditions, an army might make it over the Channel.
In the 1905 - 1912 period several very good books including John Buchan's 39 Steps, and Erskine Childers Riddle of the Sands had been based on ideas that were not beyond the bounds of possibility, in the way that General John Hacketts novels of the 1980's, and Humphrey Hawksley's of today are.
In Riddle of the Sands in 1912, the Germans were secretly building up an invasion fleet in Heligoland.
The idea was taken so seriously that there was a full scale British Army exercise in 1912, which had an enemy "German" army landing at Caister in Norfolk. It set off for London.
The British Army set off from Aldershot and marched up to the Haverhill, Newmarket area, where the first encounter "battle" took place. Beaten back it fought a fighting retreat, to the Bassingbourne area north east of Royston. This area was used for the final battle, because it was in a wide valley below a high escarpment formed by the chalk hills of the Chilterns.
The King, Generals Kitchener,French and many others watched the final battle, when off course the Brits emerged victorious. All the officers went off to a Cambridge College to have a post exercise wrap up.
My great uncle was at Trinity, in the Cambridge OTC at the time. I have his 1912 Cambridge Ordnance Survey map from the exercise which he watched whilst tearing around on a motorcycle.
Sadly this mock battle had at least two real deaths.
About a mile from Letchworth, on a country lane from Willian to Little Wymondley, is a small stone monument to two Royal Engineer Officers killed when their aircraft crashed. They had been sent out to test the theory that aircraft might have a future role to play in warfare.
As so often the British wanted to fight the war in somebody else's back yard to keep it out of our homes.
Poor old Belgium paid a heavy price.
Fiction played its part in creating the fact. Without the strong pressure of public opinion caused in part by writers like Erskine Childers, we would probably not have not have been in a place to have mobilised such an effective "Contemptible Little Army".