Battle of Alcácer Quibir
On 4 August 1578, while fighting in Morocco, young King Sebastian died in the Battle of Alcácer Quibir without an heir. The late king's elderly great-uncle, Cardinal Henry, then became king. Henry I died a mere two years later, on 31 January 1580. The death of the latter, without any appointed heirs, led to the Portuguese succession crisis of 1580. Portugal was worried about the maintenance of its independence and sought help to find a new king.