In 1306 Henry married Anne of Bohemia, sister to Wenceslaus III. Henry was then second in line to the throne of Bohemia, when he realized it he had murdered Conrad of Botenštejn. Unfortunately for both he dropped the knife on the floor and woke Wenceslaus up. Henry, angry at the solution, made an even worse plan. In the early 14th Century what we in our timeline know as Poland was unstable. Henry made a war promise to Wladyslaw I the Elbow-High. And then told Wenceslaus a lie that Wladyslaw is trying to become a king of Bohemia. Wenceslaus, still afraid from the murder, went white and ordered his troops to conquer Poland.
On 15th November, nobody in Poland expected anything, and Bohemia conquered half the Poland until 11 P.M., and on the morning of 16th November Wladyslaw rather ran away to Polish Pomerania. Henry's wife Anne overheard him and tried to stop the war, but Henry killed her and blamed it on the Polish people. This made Wenceslaus so angry, he demanded Wladyslaw a head shorter and Poland to join Bohemia. On 29th November, the war ended and the creation of Empire of Great Bohemia and Poland was finished.
Henry the Worst eventually became a king of Bohemia after Conrad of Botenštejn who escaped from prison killed Wenceslaus, but angry Conrad who didn't get his reward killed him as well.