Who is Haj Amin al Heusseini from The Haj and what is their importance?

Haj Amin al Heusseini was a Muslim fanatic, who was a major leader in the 1920 riots in protest of Jewish immigration. His goal was to take control of Palestine, but that goal was denied when he had to flee imprisonment by the British. Heusseini later returned and was named Mufti of Jerusalem.