- The advance of the French IV and XIII Corps along the Oise River is halted today by the German IX Reserve Corps, aided by the arrival of II Corps, which was pulled from the Aisne front expressly for the purpose of extending the German flank northwards. An entrenched army needs fewer soldiers per mile to hold the line, which allows both sides to send forces into the open spaces north of Compiègne without fatally weakening their existing defensive positions. Indeed, this points to one of the paradoxes of trench warfare - it was adopted in September 1914 to facilitate, not hinder, further mobile operations by making more forces available to outflank the enemy. The problem, of course, is that this is equally true for both sides, so the 'mobile' formations created by both inevitably run into each other, and trench warfare replicates itself in order to provide further 'mobile' operations. Thus trench warfare spreads like a virus along the Western Front, ironically from a desire of both sides to continue a war of movement. It also feeds the perception of the generals that trench warfare is a temporary phenomenon (i.e. present only to facilitate future mobile operations, at which point trenches will no longer be needed) as opposed to becoming a permanent fixture.
- Further east, German attacks near Rheims continue to push back the French defenders. Today the Germans seize high ground east of the city, including the forts at Berru and Nogent-l'Abbesse. The French X Corps, which had begun to march west to join the effort to envelop the German flank past 6th Army, is ordered to return to Rheims to contain the German push.
- Joffre today scales back offensive operations along the Aisne River, it becoming clearer by the day that traditional frontal assaults by infantry on entrenched and prepared German positions are not achieving significant results. Meanwhile, General Castlenau's new 2nd Army begins to assemble near Amiens.
- The redeployment of the German 6th Army is planned today at a conference at OHL in Luxembourg between Falkenhayn and Rupprecht. The first corps will arrive on September 21st and bewill be tasked with sweeping away any French infantry between Roye and Montdidier. A second corps will arrive on September 23rd, and with further units trickling in subsequent days 6th Army as a whole is to turn the enemy flank. Rupprecht, however, is concerned that the French will be undertaking similar redeployments from east to west, and will benefit from having an intact railway system to move their units faster. Thus both Falkenhayn and Rupprecht agree that German attacks must be undertaken along the existing front line to tie down French forces and prevent them from redeploying in time to stymie 6th Army. In addition to further assaults between Compeigne and Rheims, two operations are planned in the Verdun sector. The first, to be undertaken by the Crown Prince's 5th army, is to attack into the Argonne Forest to the west of Verdun. The second is an offensive aiming to drive between Verdun to the north and Toul and Nancy to the south by capturing St. Mihiel and reaching the Meuse River. To facilitate the second operation, the left wing of the 5th Army, comprising those forces southeast of Verdun, is formed into Army Detachment Strantz, named for General Hermann von Strantz, commander of V Corps. By forming this detachment, there will be a separate command staff for each attack. In addition to forcing the French to keep significant forces in the east, the operations aim to isolate the fortifications around Verdun, which are the strongest in France and form a key 'hinge' of the French line.
- General Ludendorff meets today with General Conrad at Neu Sandec in Austrian Galicia today. The relationship between the two allies is frosty at best - Conrad blames the failures of his armies in Galicia on a perceived lack of support from Germany, and spends much of the meeting lecturing Ludendorff. The German army, conversely, believes that Tannenberg demonstrates that it has done more than its share - if nothing else, Ludendorff is convinced of his own genius - and that Conrad and the Austro-Hungarian army have demonstrated particularly impressive ineptitude. Indeed, so dismissive are the Germans of their putative allies that they have not even bothered to inform Conrad that Moltke has been replaced by Falkenhayn.
Despite the atmosphere of recrimination, agreement is reached for the next stage of operations. The defeat of the Austro-Hungarian armies in Galicia potentially exposes German Silesia to Russian invasion, which necessitates a German response. Ludendorff convinces Falkenhayn that a major German force is needed immediately, so 8th Army in East Prussia is reduced to two corps and the remainder redeployed near Cracow to form a new 9th Army of four corps, a reserve division, and a cavalry division. At Ludendorff's insistence Hindenburg is to directly command 9th Army with himself as Chief of Staff, and while command of 8th Army is transferred to General Richard von Schubert, Hindenburg and Ludendorff are to remain in a supervisory role over their old command. Conrad, meanwhile, agrees to assign the Austro-Hungarian 1st Army to co-operate with the German 9th Army, while the rest of his armies, after completing their retreat, will, it is hoped, go back over on the offensive.
Falkenhayn's conception of the role of 9th Army is simply to occupy the Russians and help their Austro-Hungarian allies survive - his attention is still primarily on the Western Front, seeking a decisive decision there. Hindenburg and Ludendorff, however, believe that the most effective route to victory is on Eastern Front. Their plan for 9th Army is to undertake a major offensive to seize the Russian fortress at Ivangorod and advance on Warsaw, seeking to crush the Russian armies just as they had done at Tannenberg. They believe that they should have priority for reinforcements, and they begin bombarding not only Falkenhayn but also the Kaiser for additional units for the East. Falkenhayn thus finds the duo of Hindenburg and Ludendorff to be rivals, not subordinates, and the latter are able to leverage the prestige gained from Tannenberg to raise their profile. German high command is thus fundamentally divided on grand strategy, divided between West and East.
- In London, the British Admiralty has fallen for Admiral Spee's deception at Samoa four days earlier, and believes that the German East Asiatic Squadron is returning to the West Pacific. Today they signal Rear Admiral Craddock in the South Atlantic with revised instructions: 'Situation changed . . . Gneisenau appeared off Samoa on 14th and left steering NW. German trade on west coast of America is to be attacked at once. Cruisers need not be concentrated. Two cruisers and an armed liner appear sufficient for Magellan Straits and west coast. Report what you propose about Canopus.' Crucially, the signal says nothing about the modern armoured cruiser Defence - the Admiralty has decided that with the German East Asiatic Squadron sailing westward, it is not needed in the South Atlantic, and can be retained on its present station in the Mediterranean. Craddock, however, assumes that Defence is still on its way, believing quite reasonably that if the Admiralty had changed its mind, it would have let him know.
- In China, the main portion of the Japanese expeditionary force sent to capture the German enclave at Tsingtao lands at Laoshan Bay, thirty miles from their objective. The Japanese aim is to assemble overwhelming force, especially in terms of artillery, before advancing on the German positions.