In the course of a stubborn battle, German troops under the command of Max von Gallwitz broke into the heavily fortified defenses of the outnumbered Russian army and took the city of Przasnysz.
The Supreme Commander of All German Forces in the East, Field Marshal Paul von Hindenburg, arrived in Willenberg, at the headquarters of the Gallwitz's army group.
[5] At 10 o'clock on July 14, the German 36th Infantry Division passed Przasnysz; aerial reconnaissance reported the beginning of a mass withdrawal of Russian rears and convoys.
However, in general, rainy weather did not allow the German army to organize a quick pursuit and bring up heavy artillery in a timely manner.
[6] The German 17th Army Corps conducted stubborn attacks all day long at the junction of the 30th Infantry and 11th Siberian Rifle Divisions, captured Hill 124 near Dziki Bór.
The resumption of the offensive from 19:00 and the introduction of the 14th Landwehr Division into battle led to the coverage of the Russian 1st Turkestan Army Corps and its retreat.
[7] By the night of July 16, at the headquarters of the army group of M. von Gallwitz, the development of an operation against the Russian fortress of Novogeorgievsk and to force the Narew River began.
However, the slowdown of the offensive on the left flank caused the intervention of the chief of staff of the Supreme Commander of All German Forces in the East, Lieutenant-General E. Ludendorff: instead of a barrier at Ostrołęka, he demanded to attack the fortress.
[8] A. Litvinov, having received the necessary reinforcements, ordered from the night of July 16 the 1st Siberian and 1st Turkestan corps to go on the offensive and restore the previous situation.
At 6 o'clock, the division of Willem Clifford Cocq von Brougel broke into Ciechanów and, after a street battle, captured the city.
During July 18, the Gallwitz's group advanced after the retreating troops of the Russian 1st Army and reached the fortifications of Novogeorgievsk with the right wing, and the approaches to Ostrołęka with the left.