The placard in question is the official "Communiqué" of the Central Workers' Committee of the Polish Socialist Party (PPS) dated April 5, 1917. This document was the direct response of Polish socialists to the outbreak of the February Revolution in Russia and the declarations of the Petrograd Council of Workers' and Soldiers' Delegates on the Polish question.
The socialists pointed out that it was the "peoples united in freedom," and not the imperialist powers, who should emerge victorious from the ongoing war and shape a new order.
