In the course of time, the soldiers of various battalions prepared individual sections of the defense according to their needs, digging trenches with covered shelters and connecting ditches.

In the center of the town, on the market square, artillery and mortars were placed in dug-in positions to support the defensive lines with fire.

During the day, only observation was carried out, so the soldiers took turns resting and some of the subunit's personnel mostly operated in the surrounding area.

Bircza also had a civilian population (both residents and refugees from neighboring villages), which Ukrainian intelligence presumably used to recruit its informants.

In addition, Bircza was home to a group of demobilized soldiers from the division's units, since here they were assigned a rallying point from which they were to depart on October 23–24 for Przemyśl.

It marched in compact formation along the road from the direction of Przemyśl, thus confusing observers, and managed to approach close to the military outpost.

The core of the Ukrainian forces consisted of the "Rena", "Yara" and "Dry" units, as well as other unrecognized ones, belonging organizationally to the raiding "Podkarpacie" kuren under the command of "Prut".

The group advancing along the road from Przemyśl, despite suffering losses, broke into Bircza, killing soldiers and civilian residents they encountered along the way.

The first attack on Bircza ended inconclusively, while the Ukrainian Insurgent Army (UPA) managed to penetrate the town, causing casualties and damage, they were unable to fully capture their objectives or decisively defeat the Polish garrison.

Despite the attackers breaking into Bircza and engaging in combat for several hours, the Polish regiment's headquarters remained uncaptured, and the UPA forces eventually withdrew.

The Ukrainian Insurgent Army launched its second attack on Bircza at 22:00 on November 29, on a bright moonlit night, supported by mortar fire.

Notified by radio of the attack, the commander of the 9th DP immediately sent an emergency subdivision from Przemyśl to help, in the strength of one infantry company (about 100 soldiers) on 4 trucks, but due to the blockage of the road the unit did not reach the place.

[5] The UPA unit was commanded by Volodymyr Shchygielski, who was executed four years later in Rzeszow for the crimes of Ukrainian partisans.

A mounted maneuvering group of about 100 soldiers was also stationed in Bircza, but in the evening it left for action in Dobra Szlachecka.

Chots 504 and 505 of "Bartel" and "Chaika", which were further away, were late in their assault, having already entered the area lit by the burning building, and suffered heavy losses.

Subdivisions 505 and 506 were well lit, and attacked the brick building of the district office, located on a high slope, so they suffered heavy losses.

The Polish counterattack pushed the chotts into the defenders' abandoned trenches south of the city, from which they were finally driven out at 6 o'clock, i.e., 15 minutes after the "Orski" sotnia's attack was liquidated.

This made it possible for the defenders to go out to Valkova Mountain and to fire mortar rounds at the subunits of the "Burlaki" grouping, which was still fighting.

Even before the U-4 unit took up positions, shots rang out on the right wing, in the direction of the U-7 sotnia's march, which alerted the Polish defense.

Chota 512, advancing by leaps and bounds and partially crawling along the creek and ditches on both sides of the road, approached the MO post and church, and destroyed one bunker along with a mortar and HMG, and burned ten wooden houses.

When Burlaka noticed that the firing on the western side had fallen silent and the Poles had redeployed their forces toward him, he ordered a retreat.

Attempts were also made to cut off the unit's retreat south toward Wola Korzeniecka and Lomna, and destroy it in the open.

The condition of some of the skeletons indicated that some of those wounded in the battle had been beaten to death, or killed by a shot to the head from a short distance.

It was found that in addition to 23 UPA members, the grave contained the bodies of 5 civilians previously imprisoned in the local jail,[11] were killed the next morning.

In addition, the UPA forces suffered heavy casualties, including the deaths of Mykhailo Galyo and Dmytro Karvanskyi.

Tomasz Kolanek describes the Polish victory in Bircza as "uncomfortable ", due to the UPA's massacres on Poles continuing.