In 1914, both the French and German militaries had the same general war strategy: attack to win. This held true for their two respective military commanders also: Joseph Joffre and Helmuth von Moltke.
Joffre’s relied on tactics of unrestrained offensives in order to carry his goals, and he intended to fling his armies directly across the Franco-German border, whatever the cost . . . and indeed, that cost turned out to be high.
Moltke, however, relied upon a different sort of attack: an incredibly large flanking maneuver, called the Schlieffen Plan, functioning like a large wheel of German armies slicing Westward across neutral Belgium, turning South to bite Paris off from the rest of France, and finally heading East to take the remaining French armies in the rear. If it worked, every French army would either be out-flanked or eventually encircled.
For the first several weeks of the war (August 1-21), Moltke grew anxious for the slow advance of the German right wing. The fortified areas at Liege and Namur had dramatically slowed the German drive. As these places eventually fell to siege, however, the German advance finally picked up steam. Meanwhile, Joffre remained oblivious to the Northern threat, and remained focused on his own attacks on the Franco-German border which turned out to be entirely fruitless. By late August the French armies in the North had given much ground to the Germans, being overwhelmed, outflanked, or both.
As the war entered early September, even the begrudged assistance of the British Expeditionary Force barely slowed the rapid German advance. Nevertheless, Moltke’s forces were no longer heading in a direction to encircle Paris. Part of the Moltke’s problem was the inconsistent, warping effect of the Allied defense, but Moltke himself proved shortsighted in his tactics: he ordered the far right-wing of the German army (the First Army) to remain linked with its neighboring army to the left (the Second). As a result, the German First Army no longer had the freedom to move West in order to out-flank its opponents. Worse, Moltke began taking troops from this right wing and sending them elsewhere.
By September 9, Joffre’s French armies were in a terrible state, generally disorganized by the constant retreating and quite demoralized for the amount of their country of which the Germans had taken possession. But their delaying actions on the Germans combined with their organized retreats had gained them the opportunity to make a defensive stand. What remained of the able-bodied French troops gathered on a line near the Marne river, so naming the consequent conflict the Battle of the Marne.
By mid-September, the Allied situation was still desperate, but they had shortened their lines enough that the Germans themselves would have to dangerously extend themselves in order to continue the advance. Moltke again proved too conservative for his own good (and the good of the German goals), and he ordered a halt in order to organize the integrity of the German lines. Significantly, Joffre’s troops too had been trying to gather themselves for the integrity of a defensive line, only the German advance had been too rapid to allow for this.
Finally, in late September with the German Southward push southward stopped, Joffre could order the final stages of the retreat: small, tactical salients were abandoned in favor of creating a more cohesive line, and troops were shifted away from indefensible positions back into a better line, or perhaps even into the reserves.
Though these final movements did not represent a “retreat” in the same sense as the massive withdrawals since mid-August, they nevertheless formed the final stages of the French retrograde movements. By September 27-28, Joffre could focus exclusively on the next stage of fighting on the Western front already in progress: a race back to the North!