General von Armin (Commander of the German 4th Army) was to remain strictly on the defensive.
He was to “put in time,” to “poke,” in fact, until the big movement of troops from the East should have thoroughly reconstituted the Western Front.
We were to be allowed to waste our time and our forces in petty gains of unimportant territory, and to eat our hearts out in the slough.
To this end, and because the waterlogged soil of Flanders did not allow of the making of another Siegfried Line, the enemy had devised a new tactical method.
Directly the theory of this method is understood, many of the once puzzling circumstances of this battle become comprehensible.
It involved the use of but one comparatively new contrivance, the “pill-box.” The “pill-box,” first seen at Messines, was a small concrete fort. Sometimes it only stood up a yard or two above the ground. More often it stood well up, concealed within the ruins of a derelict farm.
It held a garrison of anything up to thirty or forty men, and bristled with machine-guns.
The tactics themselves in which the pill-boxes figured are admirably described by Mr. Buchan:
“The enemy’s plan was to hold his first line—which was often a mere string of shell-craters linked by a trench—with a few men, who would fall back before an assault. He had his guns well behind, so that they should not be captured in the first rush, and would be available for a barrage when his opponents were entangled in the ‘pill-box’ zone. Finally, he had his reserves in the second line, ready for the counterstroke before the assault could secure the ground won.... Any attack would be allowed to make some advance; but if the German plan worked well, this advance would be short-lived, and would be dearly paid for. Instead of the cast-iron front of the Siegfried area, the Flanders line would be highly elastic, but would spring back into position after pressure with a deadly rebound.”
The thoroughness and success with which this plan was carried out may be read in the story of Glencorse Wood, of St. Julien, and of many another bitterly fought “Minor Action.”