The Fellowship of the Ring by J.R.R Tolkien (Harper Collins 1991) pp.169-80
Up until this point of the journey the hobbits have been more or less “looked after”. Even though almost from the beginning their steps have been dogged by the pursuit of the deadliest of enemies in the shape of the Nazgûl of Mordor they have been able to find protection from such mighty allies as the company of High Elves led by Gildor Inglorien or Tom Bombadil in the Old Forest and the Barrow Downs. And as well as the hospitality they enjoyed in the house of Tom Bombadil and Goldberry they have been well fed and watered in the farmhouse of the Maggots and the Prancing Pony in Bree.
But now the nature of the journey makes a sudden change with the attack upon the Prancing Pony in the night. The hobbits lose their ponies and set off with a poor half-starved creature belonging to Bill Ferny, the biggest villain in the Breeland, who is certainly in league with the Black Riders and who makes as much money as he can from their misfortune.
When I say, misfortune, I mean the fact that, from their perspective, that what they thought was going to be a road journey by sturdy pony from Bree to Rivendell, has become a hard march, a yomp as soldiers call it, across hard terrain, carrying heavy loads, with no shelter. Their only pony has to carry as much food as it can take for a fortnight’s journey and the hobbits have to take the rest upon their backs. Only Strider is not much discomfited by this. For him a yomp from place to place is normal life and he has but one extra burden to carry and that is the care of four companions about whose capacity to deal with hardship he has many doubts. Butterbur has already voiced these aloud through his remark that the hobbits are acting as if they are on holiday but even with these doubts in mind Strider has already made up his mind.

“I am Aragorn son of Arathorn; and if by life or death I can save you, I will.”
The journey really begins with the crossing of the Midgewater Marshes. Tolkien never liked boggy country. I was about to say that nobody does but at one time a whole way of life was developed by people living in the fenland of eastern England or the Somerset Levels. Those who know their English history will treasure the year 877 when all that remained of free England was the Isle of Athelney hidden deep in the Somerset Levels when Alfred the Great hid there from Danish invaders. Some call this place the birthplace of England, a place so remote that the Danes could not reach it with sufficient forces to capture the king. Others will remember the last defence of Hereward the Wake against the all conquering armies of William of Normandy on the isle of Ely in the Cambridgeshire fens two centuries later when he too used the natural defence of the bog against his enemies. But a bog makes good defence because it is hard to cross by foot. I remember once having to cross one late in the day. I was grateful for the sturdy stick that I had with me. Every step that I took required a careful use of the stick to find ground firm enough to take my weight and I would often use it to swing across from tussock to tussock hoping that I would not miss my footing and find my boots and then my legs disappearing into the ooze. Recently I learned that in the trenches of the First World War British soldiers feared the mud more even than shells exploding about them and that many of them drowned in that mud.

Tolkien knew the mud of the Western Front at first hand and hated it. Is it a coincidence that two of the great journeys of The Lord of the Rings begin with a journey across marshland, the journey from Bree to Rivendell and later the journey of Frodo and Sam from the Emyn Muil to Mordor. For Tolkien nothing would better express the hardships that lay ahead. For the hobbits even the companionship of the greatest traveller of his age cannot protect them from the hardships that they must now endure.

The late Western Roman emperors relocated their capitol to Ravenna, too, for the military advantage of the surrounding mires. Lucky for the English that Alfred was a classical scholar!
Now that would suggest that Alfred’s retreat to Athelney, after Guthrum’s Christmas Day surprise attack, had been prepared to some degree. I had always thought that he was simply running for his life at this point. But there is no doubt that his communications were still in place and that he was able to raise an army to defeat the Danes.
One thing I think that we can safely say though is that nowhere in The Lord of the Rings do we see marshland as a place of defence, although it is a hard environment in which to track somebody.