Deleted member 1487
Rennenkampf was not in a position to attack, he was having serious supply issues from advancing before his supply elements were mobilized, which ended up helping doom the Russian 2nd Army to the southwest too.Not at all and there are many threads at this site that would contradict you. For example, just sending recon aircraft to the north would have told Remmenkampf to punch throught the cavalry screen and bring about a collapse
Other PODs would be Zilinsky better coordinating the offensive, the first Army delaying their movement two days or the Germans trying to retreat acrossthe Vistula which they considered after Gumbenien. And these are oly PODs post August 1914
https://en.wikipedia.org/wiki/Battle_of_Tannenberg#Main_battle:_26.E2.80.9330_August
Zhilinskiy was visited by the commander of the Russian Army, the Grand Duke Nicholas Nikolaevich of Russia, who ordered him to support Samsonov.[28] Therefore, Rennenkampf ordered two of his corps to invest Königsberg, while the other two were to march to make contact with Samsonov. These orders were sent by wireless in the clear. The next day the Russian First Army's cavalry started riding towards their Second Army, but their infantry waited for resupply.
The Russian First Army had been so slowed by the combative German cavalry screen that by the time the battle was over their closest unit was still perhaps as much as 70 km (43 mi) from the trapped Second Army. Other Russian units were scattered back along the line to Königsberg, leaving the First Army itself in a dangerously spread-out position.
Gen. Basil Guruko, commanding the Russian First Army Cavalry Division (and from 1916–17 chief of the general staff), was told later that Samsonov did not know what was happening on his flanks because he was observing the action from a rise in the ground a distance from his wireless set and reports were not relayed to him.[32] It was late in the day before he realized that his army was in frightful danger.
You're missing the point that the Russians lacked communication lines to actually coordinate once over the Prussian border beyond easily interceptable radio at the army level and courier. Rennenkampf retreating after Gumbinen would have left 2nd Army all by itself and dead like IOTL.