The victories won by the armies of the Central Powers in Gorlice–Tarnów offensive by the end of May 1915 prompted consideration of the development of success along the entire Eastern Front.

On May 28, the Chief of German Great General Staff, General of Infantry Erich von Falkenhayn, defined the tasks of the German army of the Eastern Front in continuing the offensive: as holding Libava for the longest possible time, capturing Warsaw with the help of chemical weapons, and facilitating the operation in Galicia by attracting Russian forces.

On June 2, Falkenhayn reported that the resistance of the Russian troops in Galicia had weakened, and there was no longer a need for a strike on Pilica river.

Falkenhayn this time put forward the idea of an offensive north of the Neman, using forces from the 9th Army, whose front near Warsaw was quite reliable.

The chief of staff of the 8th German Army, Colonel D. von Schwerin, who proved the unprofitability of the attack on Osowiec Fortress and offered to shift the blow to Łomża and to the west, was not listened to.

Also, Lieutenant Colonel G. Markvard, Chief of Staff of the Army Group Gallwitz, did not receive an answer about the plan to attack Przasnysz.

For this, a great military victory is needed through the close interaction of the Mackensen and Hindenburg army groups between the Bug, the Vistula and the Narew.

[11] The decision was influenced by the position of the chief of staff of the Austro-Hungarian Army Higher Command, Infantry General Franz Conrad von Hötzendorf.

[15] Russian fortified positions consisted of four defensive lines, resting against the fortresses of Novogeorgievsk, Pultusk, Różan, Ostrolenka, Łomża, and Osowiec.

[17] Opposing these forces, the German 9th Army, Field Marshal Prince Leopold of Bavaria, gradually turned into a source of replenishment for strike groups.

[18] Russian troops retained a numerical advantage over the Germans, the supply of shells made it possible to conduct an intense battle for several days.

On August 2, M. Alekseyev gave the order to stubbornly defend the line of Warsaw forts and Praga (a suburb of Warsaw on the right bank of the Vistula River), but in the evening he ordered to withdraw the 2nd Army on the night of August 3 to the right bank of the Vistula, retaining only the line of forts, but not waging a stubborn battle on it, but only, if possible, delaying the Germans.

The garrison of the Novogeorgievsk fortress, now subordinate directly to M. Alekseyev; on August 3, it began to be withdrawn from advanced positions to the forts of the outer bypass.

On August 4-5, Russian troops stubbornly defended their positions along the Orzyc river, constantly conducting counterattacks, but by the evening they were pushed back.

In the morning, the troops of the 9th German Army, led by Field Marshal Prince Leopold of Bavaria, entered the capital of the Kingdom of Poland.

The heavy casualties of the Russian 12th Army (up to 80,000 men, of which 30,000 were killed and captured) forced its commander to decide to withdraw, despite the objections the chief of the staff of the North-Western Front.

By the evening of August 10, the Russian 1st and 12th armies retreated to new positions, the Germans completely captured the Łomża fortress, and entrenched themselves on the banks of the Bug River.

Von Gallwitz was preparing to continue pushing through the junction of the Russian armies, but E. Ludendorff categorically ordered the direction of the attack to be shifted to the right flank - along the right bank of the Bug River.

On August 15, the corps of the center and left wing of the army of M. von Gallwitz reached the Myanka River, repelling Russian counterattacks and capturing 2,900 prisoners.

The quartermaster general of the staff of the army group P. von Hindenburg, Lieutenant Colonel M. Hoffman, announced a new task set by the Supreme Commander of All German Forces in the East: to reach the Riga-Grodno-Brest line.

On August 23-25, in stubborn battles with the Russian rearguards of the 1st, 2nd and 4th armies, the German troops advanced in the bend of the Narew and approached Białowieża Forest from the west.

The staff of the Supreme Commander of All German Forces in the East stated the failure of attempts to encircle the Russian armies in front of the middle course of the Bug River.

The Russian armies of the center of the Northwestern Front withdrew beyond the Bug and Narew Rivers without losing contact with each other and not allowing a deep breakthrough of the German troops.