The new 1st Army was composed mostly of former Corps-sized operational groups of Generals Edward Rydz and Józef Lasocki.

Majewski was succeeded by Gustaw Zygadłowicz (May - June 1920), then by Jan Romer (June 23–28, 1920), Mieczysław Kuliński (June 29–31, 1920), Władysław Jędrzejewski (until August 6), Franciszek Latinik (until August 22), Lucjan Żeligowski (did not assume command) and finally Gen. Aleksander Osiński (from August 23 until September 1, 1920).

The chiefs of staff were Lt. Col. Adam Nałęcz Nieniewski (April and May 1920), Col. Jan Kubin (until June 1920) and Col. Franciszek Kleeberg.

However, its forces were gradually reassigned to smaller formations and by the end of August 1920 the only division under its command was the 8th Infantry.

By August 20 the unit reached the Orzyc River near Krasnosielc and was disbanded, with the 8th Division withdrawn to Lesser Poland for regrouping.