During the Battle of the Aisne on the 16th of September, Sir John French told a hospital ward full of wounded officers that the war was “a stalemate in our favor,” causing one of them to add derisively in a letter home: “whatever that means.” In fact, after being repulsed at the Marne, the Imperial German Army had entrenched itself above Aisne, beginning the phase of the war by which we will come to know the Western Front.

Today, as the British Expeditionary Force redeploys near the English Channel in a bid to outflank the Germans, French pens a letter to his king explaining how the tactical situation has affected the strategic picture. Published on the 16th, the message is an important document for understanding why and how the armies of Europe have all begun digging in.

The position held by the enemy is a very strong one, either for a delaying action or for a defensive battle. One of its chief military characteristics is that from the high ground on neither side can the top of the plateau on the other side be seen except for small stretches. This is chiefly due to the woods on the edges of the slopes. Another important point is that all the bridges are under either direct or high angle artillery fire. The tract of country above described, which lies north of the Aisne, is well adapted to concealment, and was so skilfully turned to account by the enemy as to render it impossible to judge the real nature of his opposition to our passage of the river, or to accurately gauge his strength; but I have every reason to conclude that strong rearguards of at least three army corps were holding the passages on the early morning of the 13th.

[…] Throughout the whole course of the battle our troops have suffered very heavily from (siege artillery) fire, although its effect latterly was largely mitigated by more efficient and thorough entrenching, the necessity for which I impressed strongly upon Army Corps Commanders. In order to assist them in this work all villages within the area of our occupation were searched for heavy entrenching tools, a large number of which were collected.

[…] Sir David Henderson and the Royal Flying Corps under his command have again proved their incalculable value. Great strides have been made in the development of the use of aircraft in the tactical sphere by establishing effective communication between aircraft and units in action.

[…] It…became essential to establish some system of regular relief in the trenches, and I have used the infantry of the 6th Division for this purpose with good results. The relieved brigades were brought back alternately south of the river, and, with the artillery of the 6th Division, formed a general reserve on which I could rely in case of necessity. The Cavalry has rendered most efficient and ready help in the trenches, and have done all they possibly could to lighten the arduous and trying task which has of necessity fallen to the lot of the Infantry.

[…] Our experiences in this campaign seem to point to the employment of more heavy guns of a larger calibre in great battles which last for several days, during which time powerful entrenching work on both sides can be carried out.

French is a general at a time when they rarely get to see the battles they fight because the armies they command are so enormous. Indeed, everything he has to say to his king today is based on reports he has received, not firsthand witness. French’s account fairly glows with positive assurances, but in fact the Battle of the Aisne has been an undisputed German victory. The BEF has fought off counterattacks, to be sure, but none of its attacks have succeeded, either.

Over 13,500 British troops have died since the 12th of September — a casualty rate that has only diminished because French pulled his troops from the front line to redeploy them north. He says nothing of his slow progress from the Marne, a tardiness that his counterpart Joseph Joffre did not miss, and which may very well have allowed the German army to escape destruction.

Yet underneath the ass-covering, we can still discern trends that have taken over the war: constant trench-digging; fighting from cover and concealment; the arrival of high-angle gun tubes that can plunge fire into trenches; the integration of aircraft; a regular rotation of troops at the front line; cavalry fighting dismounted; days-long bombardments intended to soften up the enemy before a charge.

The late German General Schlieffen’s greatest fear — that his plan for rapid victory in France will bog down into a protracted stalemate — has come true: “All along the line the corps will try, as in siege warfare, to come to grips with the enemy from position to position, day and night, advancing, digging in, advancing again, etc., using every means of modern science to dislodge the enemy behind his cover.” He might was well have been talking about Sir John French, who will spend the next two years adapting to this new kind of war at a tremendous cost in British lives.