The kingdom of Poland was established, in 1815, as part of the Russian Empire. During WWI, Poland was occupied by the Central Powers. The northern half by Germany, the southern half by Austria. In the aftermath of WWI, Poland annexed parts of both Germany and Austria. Referendums were held in Allenstein, Marienwerder and Upper Silesia, that chose to stay German. Eastern Silesia was divided between Poland and Czechoslovakia, the Czechoslovakia part being annexed by Poland in 1938. Orawa and Spizs were awarded to Poland. On the Russian border the situation was complex. In the wake of the Russian Revolution, and the civil war that followed, Belarus, Ukraine and Western Ukraine had declared independence. The Polish army played an active role in the struggles of the time, advancing far into Russia. In the Baltic, Central Lithuania declared independence with the intent to become part of Poland. By 1923, Poland had annexed large parts of Russia. The first Polish stamp was a single issue in 1860. As Poland gained independence, stamps were issued in 1918/1919 for the different parts of Poland that had different currencies as a result of the occupation by the Central Powers. General issues followed in 1920. In this period many cities issued local provisionals.