The battle of the Ourcq River, 5-9 September 1914 (First World War) was part of the wider First Battle of the Marne. The German 1st Army, under von Kluck, made up the right wing of the great German advance into France. By the start of September it was moving south, just to the east of Paris, as part of the German advance that threatened to envelope the French armies to the east. However, a gap was beginning to develop between the 1st and 2nd Armies. This gap would be the target of the great Allied counterattack on the Marne and the threat it posed to the German 2nd Army would play a major part in the German decision to retreat.
The extreme right flank of the German advance was protected by the German IV Reserve Corps under General von Gronau. The French command-in-chief, General Joffre, planned to concentrate against the 1st army. Part of that plan would involve an attack by the French 6th Army under General Maunoury, with support from General Gallieni, the military governor of Paris, against the exposed flank of von Kluck’s 1st army.
The battle of the Ourcq did not go entirely to plan. Von Gronau detected the French advance on 5 September, and launched a counterattack that delayed the French attack and allowed von Kluck to move his II Corps north west, from its position south of the Marne to one west of the Ourcq. Over the next three days the rest of the 1st Army would follow. The French were now attacked a major German formation and not the reserve corps they had expected to be facing. Maunoury’s Sixth Army found itself outnumbered and in danger of being enveloped. It was this battle that saw the famous incident in which reinforcements were rushed to the front from Paris in taxi cabs.
By the end of 8 September, von Kluck was ready to launch his own counterattack on his right flank. An initial attack by the IX Corps under General von Quast achieved some local success and even appeared to threaten Paris. However, the situation further along the German line was not so promising. As von Kluck had moved west onto the Ourcq, the gap between the 1st and 2nd armies was forty miles wide. Allied troops, amongst the BEF, were advancing into the gap.
The commander of the 2nd army, General von Bülow, felt that his position was dangerously exposed. On 8 September Moltke dispatched a staff officer, Lieutenant-Colonel Richard Hentsch, to investigate the real situation at the front. He had agreed with von Bülow’s views, and recommended a withdrawal back behind the Marne. On 9 September, von Bülow learnt that four enemy columns were marching through the gap toward the Marne and decided to order a retreat. Once the 2nd army was on the move, von Kluck had no choice but to follow. Over the next five days the Germans pulled back from the Marne to the Aisne.
The fighting on the Ourcq had failed to achieve its initial objective, to outflank the German 1st Army, but by drawing von Kluck north west when he should have been moving south it helped to create the fatal gap in the German line that helped create the miracle of the Marne.