- French cavalry this morning observe German infantry and cavalry of 1st Army advancing towards Compiègne, which is not in the direct line towards Paris. It is the first indication of the 'inward turn' of Kluck's 1st Army. Of greater concern to Joffre in the moment are reports this evening that German cavalry have crossed the Oise River south of Noyon, moving into the precise gap in the French line between 5th and 6th armies opened by the retreat of the BEF. At Joffre's headquarters, he and his staff weigh their options. Vanished are the grand offensive undertakings of Plan XVII - instead, the emphasis is on mere survival. The question now is how much territory must be given up before the French armies are able to stand and fight the Germans.
- In London Lord Kitchener, British Secretary of State for War, receives an alarming report from Field Marshal French today. In it the commander of the BEF states his intention to take his force out of the front line, retiring behind the Seine River and maintaining a considerable distance from German forces. He states bluntly that he no longer believes the French army can triumph, and the preservation of the BEF as Britain's only field army is behind his decision to retreat out of harm's way.
Kitchener reads the report with astonishment and dismay. French's proposed course of action would amount to desertion of their ally, and render null the entire basis for Britain's entry into the war in the first place. Moreover, it would leave an immense gap between the French 5th and 6th armies, giving the Germans the chance to envelop and crush them. A Cabinet meeting is summoned at which Kitchener bluntly states that the retirement of the BEF will lose the war. He is authorized to inform Sir John French that he should conform to the plans of Joffre, and raised questions regarding the impact of the retreat of the BEF on the French line.
Late tonight, Kitchener is at the War Office, awaiting French's reply. So anxious is the Secretary of State for War that he has the decoders pass the message word by word as it comes through. French's telegram reiterates his previously-stated plans, and makes clear his disdain for his allies. He understood that the retreat of the BEF would open a gap in the French line, but 'if the French go on with their present tactics which are practically to fall back right and left of me, usually without notice, and to abandon all idea of offensive operations . . . the consequences should be borne by them , , , I do not see why I should be called upon to run the risk of absolute disaster in order a second time to save them.' Beyond the bald-faced lie regarding offensive operations, given that French had forbidden Haig from aiding Lanrezac's 5th Army at the Battle of Guise, it is clear that the BEF commander remains determined to retire from the battlefield.
- The last Russian units of 2nd Army surrender today, bringing the battle to a close. Hindenburg decides to call the victory the Battle of Tannenberg, after a nearby village where Teutonic Knights had been defeated by Slavs in 1410. Tannenberg is not only seen as redemption, but deliverance. The spectre of Russian hordes sweeping over East Prussia has hung over Germany for a month, and now the threat has been annihilated. It is the most lopsided victory either side will achieve in the war - the Germans capture 92 000 prisoners and 400 artillery pieces, while approximately 30 000 Russians are killed. Two entire Russian corps, and most of a third, simply cease to exist. The triumph make Hindenburg and Ludendorff overnight heroes in Germany, and the decisive victory on the Eastern Front stands in contrast to the continuing campaign in the West.
After its crushing victory at Tannenberg, OHL issues new orders for 8th Army - it is to concentrate on clearing East Prussia of the enemy; operations in Russian Poland will wait until this is completed. As such, the new priority of 8th Army is to attack the Russian 1st Army, still in East Prussia.
- Along the Galician frontier the Russian 5th Army is able to escape its potential encirclement today. The Austro-Hungarians do not prove as resolute as the German 8th Army in Poland - false reports of Russian reinforcements paralyze the two arms of the pincers, leaving a 32-kilometre gap through which the 5th Army retreats. The Battle of Zamość-Komarów is undoubtedly an Austro-Hungarian victory, as the Russian 5th Army has suffered 40% losses and been forced back. However, it is not a decisive victory in the style of Tannenberg - 5th Army remains in the field.