and the ultimate recapture of Lemberg, which would sever lines of communication between the Russian Northwest and Southwest Fronts. Mackensen would not only command his Eleventh Army but also the Austro-Hungarian Fourth Army, augmented with the X and XVII Corps, on his northern flank, and the Austro-Hungarian Second Army, augmented with the Beskidenkorps, on his southern flank. The Eleventh Army Order of battle, north to south, consisted of Karl von Behr's Corps, Emmich's X Corps, Eugen von Falkenhayn's XXII Reserve Corps, Plettenberg's Guards Corps, Arz's Austro-Hungarian VI Corps, and François' XLI Reserve Corps. The attack commenced on 13 June, and by 17 June, the Germans had pushed the front line back to positions near Gródek. The German attack commenced again on 19 June, after the previous day was spent bringing forward their heavy artillery with matching aerial reconnaissance. The Russians reverted to a headlong retreat, and on 21 June the Grand Duke Nicholas ordered abandonment of Galicia. On 22 June Mackensen's Austro-Hungarians entered Lemberg after an advance of , an average rate of per day. The Galician oil fields, crucial for the German navy, were soon back in production and 480,000 tons of badly-needed oil was captured. Casualties and losses The battles on the rivers Bug and Zlota Lipa ended the Gorlice–Tarnów offensive, during which the armies of the Central Powers managed to inflict the largest defeat on the troops of the Russian Empire. The operation, which lasted 70 days, in terms of the number of troops involved (taking into account the replenishment of combat and non-combat сasualties - 4.5 million men on both sides), in terms of сasualties incurred by the parties (on both sides more than 1.5 million men), in terms of trophies, became the largest in during the First World War. Heavy сasualties in the May battles forced the Russian armies to retreat from Galicia in early June 1915, and so hastily that the fortified positions prepared in the rear remained abandoned. The low stability of the troops of the 8th Army, which left Lvov on June 22, became the reason for sharp reprimands from the front headquarters. In the Russian armies south of the Pilica River, 26 infantry divisions were transferred and put into battle in 70 days, two more guard divisions remained in reserve. But for the armies of the Central Powers, the victory came at a high price. The arriving reserves (6.5 divisions) brought