- Northwest of Warsaw, the German forces under General Gallwitz have advanced only five miles since their offensive was launched on the 13th. However, the response of the Russian army commanders on the scene has been to emphasize a forward defence by their infantry, which has meant in practice that the Russian soldiers have suffered terribly under German artillery fire; seventy percent of the Russian forces opposite the German advance on the 13th are casualties by today. In this way the Germans are achieving their objective of grinding down the Russian army. Faced with such enormous losses, Alexeiev of North-West Front orders 1st and 12th Armies to pull back behind the Narew to the southeast, and make a new stand along the river line. Gallwitz, as well as Falkenhayn, conclude that the heavy Russian casualties will now allow for a breakthrough of the Russian line here and a rapid advance to and the capture of Warsaw.
Notably, the southernmost corps under Gallwitz have now reached the outer defensive lines of the Russian fortress at Novogeorgievsk, near the confluence of the Narew and Vistula Rivers. A massive defensive complex that included 1680 artillery pieces and over a million shells, Novogeorgievsk was seen as a lynchpin of the Russian defensive position in Poland. Moreover, it was only the most prominent of a string of Russian forts that had been constructed near the border in Poland for precisely the emergency that the Russian army now faced: having to retreat and needing points which could impede the enemy advance and on which the Russian army could rally. These forts, however, as with the prewar fortifications in France and Belgium, had been designed and constructed to counter artillery of an earlier age, and it remains to be seen whether Novogeorgievsk will be another Przemysl or Antwerp.
- To the south, the forces under General Woyrsch in southeastern Poland west of the Vistula River, launch their attack after a twenty-four hour artillery bombardment which has concentrated in the final hours on the Russian positions at Sienno. Here the German 3rd Landwehr Division, spearheading Woyrsch's attack, smashes through the enemy trenches and advancing six kilometres to reach the Krepianka River between Krepa and Rzeczniow. The assault has blown a hole ten kilometres wide in the Russian line, and Woyrsch issues orders to exploit the advantage with a rapid advance towards the Ilzanka River tomorrow.
|The advance of the German force under General Woyrsch, July 17th to 31st, 1915.|
- Further east the offensive of the German 11th Army continues, and this evening the Guards Corps breaks through the Russian line at Krasnostaw and secures a bridgehead on the east bank of Wieprz River, turning the flank of the Russian III Caucasian Corps to the south.