[Sidenote:  Strategic value of hills of Orxois.]

North of the Ourcq, indeed, the last heights of the Orxois form another chain of hills, from four to six kilometres wide—­the last obstacle before we come to the plateau of the Soissonnais.  These hills are of the greatest possible diversity of shape and vary in height from 200 metres at the western extremity to 230 at the eastern.  Their bases consist largely of sandstone and Fontainebleau sand, with clumps of forest scattered here and there; higher up is the softer limestone, the land being entirely cleared and covered with crops.  Here and there we find the remains of the former covering of clay and Fontainebleau sand—­wooded ridges which expand toward the east into the wood of Seringes, the forest of Nesle, and Meuniere wood.  These hills, the last as we travel northward, where they command the whole of the Soissonnais, have therefore the greatest strategic value, particularly the positions of Hartennes, Plessier-Huleu, and Seringes.

[Sidenote:  The French approach from the west.]

Luckily these formidable defensive positions were approached from the west, astride the ridges.  Starting from the forest of Retz, the French crossed the Savieres with a rush, and in a single bound reached Noroy-sur-Ourcq and Villers-Helon, which lie along one of the ridges, surrounded by orchards.  On July 19 they had advanced three kilometres to the east; the strong line of the Ourcq was outflanked.  On the 20th they were at Parcy-Tigny and Rozet-St.-Albain, pushing forward over the broken ground planted with sugar-beets and cereals, enlivened in spots by small clumps of trees perched on the sandstone hillocks.  Thus they drew near to the heart of the position—­the ridges of Plessier and of Hartennes.  There the resistance was much more violent; but after three days of hard fighting, the French entered Plessier and approached the village of Oulchy-la-Ville, surrounded by picturesque heaps of sandstone blocks mingled with pines and birches.  On the 25th, in the evening, they were in occupation of Oulchy-le-Chateau, which lies in a charming vale running down to the Ourcq.  The line of the Ourcq, as to that portion where the river, flowing between high cliffs, constitutes a real obstacle, was in the Allies’ hands.

[Sidenote:  Fere-en-Tardenois and Sergy.]

It remained to complete the victory by the conquest of the eastern sector of the hills; and this again was no easy task.  The French and Americans had now to approach that strong defensive position from the south.  On the 28th they entered Fere-en-Tardenois; the Americans crossed the Ourcq, taking Sergy, which changed hands nine times.  On July 31, after more titanic battles, they wrested Seringes from the foe.  On August 1 there was a general advance all along the line, and the Allies carried the whole line of hilltops, from Plessier-Huleu to Meuniere wood.

[Sidenote:  Heroes of the second battle of the Marne.]