The Pocket is Closed
With the capture of Chelm and Lublin by von Denta's 2nd Army, a blunder was enacted by the Russian Army that could single-handedly win the war for the Central Powers. The capture of the two areas left isolated the Russian town of Siedlce, occupied by no less than 410,000 soldiers. To the north and west were 240,000 of Paul von Hindenburg's German veterans in Warsaw, Radom and Lomza.
Essentially, over one-third of the entire Russian Army was trapped.
Von Denta, with 160,000 men, attacked the pocket. The Russians suffered massively from disease, and with the lack of a supply line and with horribly limited supplies and weapons, fighting was almost impossible for the half-million men surrounded by their enemies. Fighting proper started on September 12.
Russian soldiers abandoning their positions, September 13
Despite early advances in the battle, the fighting proved surprisingly more difficult than initially expected. The Austrians made very little ground, and von Hindenburg's troops to the north and west were unable to attack due to severe manpower gaps caused by previous battles that had yet to be filled by reinforcements.
Von Denta abandoned his attack on the 16th. Almost immediately afterwards, the 410,000 Russians in the pocket counterattacked the 90,000 men in the Chelm area. General von Vares, leading the defense of the area, ordered the area to not be given up. However, after losing nearly 10,000 men in three days, he obliged to his subordinate officers' pleas and retreated south back to Przemsyl.
General von Vares orders a retreat, abandoning the freshly-captured
defenses at Chelm in the face of a huge counterattack
However, von Hindenburg did not hear of von Vares' retreat from Chelm and the failed attack on Siedlce; he began his attack on October 6. After hearing of this, von Denta immediately ordered Vares' badly mauled corps back north to Chelm, while his own corps joined the fighting alongside the Germans against the still-trapped Russians in Siedlce.
Von Denta's men, supplanted by a huge number of men a part of Hindenburg's Army, quickly ground down the Russians, having run dangerously low on supplies and provisions in two consecutive battles. By October 9, the pocket was closed, and 410,000 Russians were lost to the Austrians and Germans.
The pocket is eliminated
The Russians staggered back from the devastating blow. Now largely outnumbered by the Germans and Austro-Hungarians, the Russians struggled to survive against the combined attacks from it's two enemies. Hotin, in the south, was taken, and mass attacks from Tarnopol threatened to break the Russian front line in half. Now, to the commanders of the Imperial Military, it was only a matter of time.
The Empire of Austria-Hungary, c. November 5, 1915
As of November 5 1915
Est. Austro-Hungarian Killed: 17,000 (152,000 total)
Est. Russian Killed: 450,000 (624,000 total)
Est. Italian Killed: 23,000 (90,000 total)
TOTAL KILLED: 490,000 (1,112,000 total)