After the armistice in Trier was concluded, the Polish government began to exert informal pressure on the Commissariat of the Supreme People’s Council to send military support for the besieged Lviv. Ultimately, a volunteer draft was announced in all military districts of the region (42 people from each district, including one master corporal and four corporals). The formation was supposed to take place in the 1st Reserve Regiment in Poznań. In total, the establishment of two rifle companies commanded by officers chosen by lot from among volunteers was planned. This was supposed to be an army which was completely ready to depart for combat, having two sanitary non-commissioned officers and eight porters in its ranks, ammunition and food supply trains, a sanitary vehicle, field kitchen, etc. Additionally, the companies were to receive four heavy machine guns. Ultimately, significantly fewer volunteers than expected were registered.

On 9 March 1919, a company which consisted of 204 soldiers set off for Lviv. It was commanded by two second lieutenants: Jan Ciaciuch and Maksymilian Soldenhoff. After a solemn farewell at the Poznań railway station, the Volunteer Poznań-Lviv Company arrived through Warsaw and Przemyśl to Sudova Vyshnia, where it was subordinated to General F. Aleksandrowicz. The task of the entire group was to break through the Ukrainian ring in that area by driving out the besiegers from their positions to the north, east and south of Sudova Vyshnia. As early as 16 March, the company of Poznań region soldiers attacked the village of Dolgomostiska, took it after two hours of fighting and opposed the Ukrainian counter-attack the next day. Two days later, battles took place in the area of Horodok, and near Melnik, the company lost 8 soldiers under heavy fire, 21 soldiers were wounded and 3 were missing in action. After dark, the company reached Horodok. During these battles, the Greater Poland inhabitants captured two cannons, one mortar and two machine guns. On 19 March, the company commander and officers received congratulations from three generals: Iwaszkiewicz, Rozwadowski and Aleksandrowicz as well as the heads of their staff. On 29 March, the company was sent to Lviv, where it met with an enthusiastic reception. Then, until the middle of July, the unit participated in battles which took place in the vicinity of Lviv, as part of the 1st Lviv Rifle Regiment. Its combat trail included the vicinity of Lviv, Zarudtsi, Novyi Yarychiv, Zalissya, Nilno, Velyka Berezovytsia, Zbiriv and Oliyv. On 7 July, Gen. Wacław Iwaszkiewicz issued a ”Laudatory appreciation”, emphasising the fact that from the very first days of fighting for Lviv, this unit was “a paragon and example for all other units through its valour and discipline.[...] I did not receive any complaints related to this company from civilians, which I attribute to its high civic sense.[...] Glory to you, brave sons of Greater Poland!”. On 29 July 1919, the company was assigned to the Greater Poland Group and on 6 August, it left for Poznań. One officer -J. Ciaciuch (M. Soldenhoff stayed in hospital as he was ill) and 225 privates returned from fighting near Lviv. 11 soldiers were dead, 58 were wounded, 7 were taken into captivity – all in all, the losses amounted to one quarter of the human resources of the unit. All officers and privates in the company were given the Cross of Lviv Defence on 1 July 1919 “for bravery and hardship in combat, for the integrity and independence of the Republic of Poland during battles for the defence of Lviv from 12 March till 1 July 1919” by the Supreme Command of the Polish Armies. The older soldiers were soon dismissed and transferred to the reserves, and the recruits were deployed in different regiments; Jan Ciaciuch returned to his original 10th Greater Poland Rifle Regiment.