Valdemar IV was a king of Denmark who reigned from 1340 to 1375. He is often referred to as Valdemar Atterdag, which means "Valdemar the Day Reborn." His reign is noted for efforts to restore the power and territory of Denmark after a period of decline. Valdemar IV successfully reclaimed lost lands and strengthened the monarchy. During his rule, Valdemar IV also focused on economic recovery and trade. He established alliances and improved relations with neighboring regions, including Sweden and Norway. His leadership helped lay the groundwork for the later unification of the Scandinavian countries under the Kalmar Union.