During World War I the Sejny-Suwałki region was occupied by German troops. Those terrains were an object of Polish-Lithuanian disputes on national grounds. In November 1918 the German occupation authorities consented to the establishment of the Interim Civic Council of the Suwałki Region, that is, the Polish civilian administration in the Augustów, Sejny, and Suwałki counties. After the evacuation of the German troops in July and August 1919 connected with the defeat of the Central Powers the issue of the affiliation of those lands was discussed during the Paris Peace Conference. The Foch line, a temporary demarcation line, was proposed. But the Lithuanians did not fully abide by those decisions, for instance, they did not retreat from Sejny.
Retreating from Sejny, on 10 August 1919 the German authorities gave the administration into Lithuanian hands [...]. The insurgents arrived in Sejny in the morning of 22 August [...]. The crack of the Polish machine guns and the whistle of the bullets were the sweetest music [...] to the ears of the oppressed population
The uprising broke out on the night of 22–23 August 1919. On the first day the Poles, led by Sublieutenant Wacław Zawadzki, took control of the main target, Sejny. Two days later the Lithuanians, aided by German volunteers, launched a counterstrike and forced the insurgents to retreat from the town. Sublieutenant Zawadzki, who commanded the defense, died. After the reorganization of the detachments and the arrival of the reinforcements from Krasnopol, the Poles launched a counterstrike and by around 11 o’clock the entire town had again fallen into Polish hands. On 28 August the Lithuanians made the last attempt to take back Sejny. That attack was repelled by Polish detachments aided by a battalion of the 41st Infantry Regiment. The Lithuanians retreated beyond the Foch line and the fighting subsided.
