That same year Albert was compelled to recognise Danish rule over lands they had conquered in Estonia and Livonia. Albert had sought the aid of King Valdemar of Denmark to protect Riga and Livonian lands against Liv insurrection when reinforcements could not reach Riga. The Danes landed in Livonia, built a fortress at Reval (Tallinn) and set about conquering Estonian and Livonian lands. The Germans attempted, but failed, to assassinate Valdemar. Albert was able to reach an accommodation with them a year later, however and, in 1222, Valdemar returned all Livonian lands and possessions to Albert's control.