Resenting his father's favouring his illegitimate half-brothers,
          Alfonso, the son and heir, started a revolt against his father and
          moved an army towards Lisbon, ready to do battle. However, his mother,
          by moving between the two armies, forced an uneasy peace between
          father and son which lasted until Diniz died and Alfonso IV became
          king of Portugal. Nevertheless, as king he continued his vendetta
          against his half-brothers, beheading one and confiscating all the
          property of another who had escaped to Castile.
              He arranged a marriage for his daughter Maria to King Alfonso XI
          of Castile. Unfortunately this turned out to be a most unhappy
          marriage as the Castilian king not only favoured a mistress, Leonor de
          Guzman, but also treated his wife cruelly. To protect his daughter,
          Alfonso IV was ready to invade Castile. Although his mother again
          intervened, her death the same year, removed a great influence for
          good in Portugal.
              In 1340 Moors came from Africa to support those in Granada, this
          removed the differences between Portugal and Castile. Jointly they
          attacked the enemy and, at the battle of Salado on 29 October 1340, he
          earned the nickname of 'the Brave'.
 

Source: Leo van de Pas