September 16th, 1915

- Though he has been slow to react to the German flank attack through Sventsiany, General Alexeiev of West Front now recognizes the threat that the enemy offensive poses: if the Germans cannot be halted, they can envelop the northern wing of 10th Army and win yet another great victory.  To counter the threat, Alexeiev has ordered Russian withdrawals to the south of Vilna to free up forces to redeploy to counter the German attack and cover the gap between 10th and 5th Armies.  Though the retreats ordered by Alexeiv allow the German 8th and 12th Armies, as well as the army group under Prince Leopold, to gain further ground and reach Baranovitchi and Lida, it has freed six corps, which are formed into a new 2nd Army east of Sventsiany to link 10th and 5th Armies.

Ludendorff, meanwhile, works to feed more divisions into the gap north of Vilna, but the the infantry cannot advance at the same pace as the cavalry.  Further, Eichhorn's 10th Army has suffered fifty thousand casualties, mainly in frontal attacks on Vilna, over the past two weeks.

- On the Eastern Front, the Austro-Hungarian 4th Army is under increasing pressure from the Russian 8th Army, and its reserves are issued contradictory orders in rapid succession in efforts to counter the latest enemy advance.  The Austro-Hungarian 2nd Division, for instance, which had been ordered south to reinforce 2nd Army after the collapse of its V Corps on the 13th, is today directed to retrace its steps back north towards the threatened northern wing of 4th Army.  Exhausted, some of the infantry collapse by the roadside, and its arrival will be delayed by several days.  In the meantime, Russian forces on the lower Stubiel River attack the Austro-Hungarian 24th Division, and break through its left wing.  Without reserves available, a counterattack can not be organized in time, and the Russians are able to consolidate their gains, which threaten the southern flank of the Austro-Hungarian 62nd Division near Cuman.

To the south, General Ivanov of Southwest Front orders the 9th and 11th Armies to halt their advance against the Austro-Hungarian armies opposite.  Their attacks had been initially undertaken to take pressure off of the Russian 8th Army to the north, and with the latter now undertaking its own counteroffensive, their operations are no longer deemed necessary.

- After a week's leave, his first of the war, General Mackensen reports to OHL headquarters on the Eastern Front at Allenstein, East Prussia, where he formally receives his orders for the forthcoming Serbian campaign: 'to defeat the Serbian army wherever he finds it and to open and secure land communications between Hungary and Bulgaria as quickly as possible.'

- Lead elements of the British 6th Indian Division reach Sannaiyat on the Tigris River today, though the arrival of the remainder, and in particular the division's artillery, has been delayed by the low water level of the Tigris and a lack of overland transport.  For the first time in the Mesopotamian campaign, however, General Townshend has aircraft available to conduct reconnaissance of enemy positions, the first three Martinsyde aircraft having arrived at Basra on August 28th.  Their reports inform Townshend that the Ottomans have established a strong defensive position just east of Kut-al-Amara at al-Sinn, where trench systems are interspersed with impassable marshes.  Townshend decides to await the concentration of his division before ordering an assault.  Though invaluable, the reconnaissance missions of his aircraft are not without risk - today one is forced to land behind enemy lines, and the Australian pilot and the British observer are taken prisoner.