sentences:  Most of the Masovian inheritance (except Czersk, who was already given to Konrad III as hereditary fief in 1495) was seriously threatened by the Kingdom of Poland at the time of Konrad III's death, and wasn't secured in his sons' hands until 14 March 1504, when by a ruling of King Alexander (who feared the protest of the local nobility) the young princes received their whole patrimony as a fief.Janusz III and his brother took the government in 1518, due to the constant riots of the local nobility.Despite this, Anna Radziwiłł retained the real power in Masovia until her death in 1522.