The Union of Horodło or Pact of Horodło was a set of three acts signed in the town of Horodło on 2 October 1413. The first act was signed by Władysław II Jagiełło, King of Poland, and Vytautas, Grand
Mound of the Horodło Union; the monument was built in 1861 in Horodło to celebrate the 448th anniversary of the union.
The szlachta were the hereditary noble estate in the Kingdom of Poland, the Grand Duchy of Lithuania, and the Polish–Lithuanian Commonwealth. It was the dominating social class in the Kingdom of Polan
Szlachcic sejmik representative Tadeusz Rejtan (lower right), with szlachta republican right of ending any Senate (Sejm) session and nullifying any legislation passed (Liberum veto), defying Russian, Prussian, and Austrian autocratic might to cease legalization of the First Partition of Poland, by halting the Partition Sejm's exit from the Senate chamber on 30 September 1773, in effect proclaiming, "Murder me, not Poland." Painting by Jan Matejko, 1866