The Germans reached the Vistula River on 9 October.
 The few Russian bridgeheads on the west bank were invested.
 Their left flank, August von Mackensen’s  XVII Corps, continued to march north until it was 19 km (12 mi) from  Warsaw.
Only small Russian pockets remained on the west bank; they were excellent targets for the German artillery.
 General Nikolai Ruzsky, commander of the Russian Northwest Front, sent troops from Warsaw to attack XVII Corps on the German left flank.
Orders found on the body of a Russian officer revealed that 14 Russian divisions were concentrating against Mackensen’s five divisions.
The Germans were also privy to Russian movements from intercepted wireless messages.
 Unlike the messages sent in the clear during the first weeks of the war, now they were in the new Russian code, which by the end of September had been broken by a German reserve officer, Professor Deubner.
  Three Russian armies were concentrating against German Ninth Army, relieving the pressure on the Austro-Hungarians in the south.
The Germans  were impressed by the plan, which they attributed to the Grand Duke, to encircle Ninth  Army by the thrust from the north into their rear.
   To prevent this XVII Corps must be reinforced.
 The Germans wanted the Austro-Hungarians to provide troops  to be hurried to the threatened flank, but the Austro-Hungarians  did not want to mingle their men with the Germans, so instead they agreed to take over the line on the German right flank.
 The released Germans were then moved north, but arrived too late for a prompt, devastating counterattack while the Russians were still concentrating.
 On 18 October Mackensen withdrew to  a defensive line 75 km (47 mi) west of Warsaw.

The Austro-Hungarian First Army, which was taking over the German right flank, was unable to  defend the crossings over the Vistula.
 The Germans claimed that they deliberately allowed the Russians to cross, then intending to engulf them.
According to the  Austro-Hungarians they  arrived too late  to prevent  the crossings.
In any event, the Russians were able to bring enough men quickly over the river to force the Austro-Hungarians to retreat to a line  60 km (37 mi),to the west.
According to Max Hoffmann, the third ranking member of Ninth Army Staff,  they pulled back without  alerting the nearby German units—they escaped only because they were warned by  German telephone operator.
  In fact the Austro-Hungarians did properly inform their allies   In this operation the Austro-Hungarians lost 40,000 men.

On 27 October, Ninth Army was ordered to retreat back into Silesia.
 The explosive-packed bridges and railways were demolished.
By 30 October the battle was over.
The Germans reached the Vistula River on 9 October.  The few Russian bridgeheads on the west bank were invested.  Their left flank, August von Mackensen’s  XVII Corps, continued to march north until it was 19 km (12 mi) from  Warsaw. Only small Russian pockets remained on the west bank; they were excellent targets for the German artillery.  General Nikolai Ruzsky, commander of the Russian Northwest Front, sent troops from Warsaw to attack XVII Corps on the German left flank. Orders found on the body of a Russian officer revealed that 14 Russian divisions were concentrating against Mackensen’s five divisions. The Germans were also privy to Russian movements from intercepted wireless messages.  Unlike the messages sent in the clear during the first weeks of the war, now they were in the new Russian code, which by the end of September had been broken by a German reserve officer, Professor Deubner.   Three Russian armies were concentrating against German Ninth Army, relieving the pressure on the Austro-Hungarians in the south. The Germans  were impressed by the plan, which they attributed to the Grand Duke, to encircle Ninth  Army by the thrust from the north into their rear.    To prevent this XVII Corps must be reinforced.  The Germans wanted the Austro-Hungarians to provide troops  to be hurried to the threatened flank, but the Austro-Hungarians  did not want to mingle their men with the Germans, so instead they agreed to take over the line on the German right flank.  The released Germans were then moved north, but arrived too late for a prompt, devastating counterattack while the Russians were still concentrating.  On 18 October Mackensen withdrew to  a defensive line 75 km (47 mi) west of Warsaw.
The Austro-Hungarian First Army, which was taking over the German right flank, was unable to  defend the crossings over the Vistula.  The Germans claimed that they deliberately allowed the Russians to cross, then intending to engulf them. According to the  Austro-Hungarians they  arrived too late  to prevent  the crossings. In any event, the Russians were able to bring enough men quickly over the river to force the Austro-Hungarians to retreat to a line  60 km (37 mi),to the west. According to Max Hoffmann, the third ranking member of Ninth Army Staff,  they pulled back without  alerting the nearby German units—they escaped only because they were warned by  German telephone operator.   In fact the Austro-Hungarians did properly inform their allies   In this operation the Austro-Hungarians lost 40,000 men.
On 27 October, Ninth Army was ordered to retreat back into Silesia.  The explosive-packed bridges and railways were demolished. By 30 October the battle was over.
Battle of the Vistula River