What is the biography of Omar ibn al-Khattab?

Umar ibn al-Khattab al-Adawi al-Qurashi, Abu Hafs, Amir al-Mu'minin (Commander of the Faithful), was born four years after the Fijar War. His mother was Hantamah bint Hisham al-Makhzumiyah. He was harsh towards the Muslims, then he embraced Islam, and his conversion was a triumph and a relief for them. He assumed the Caliphate after Abu Bakr al-Siddiq, and his reign witnessed many conquests. For more information, refer to "Al-Isabah" by Ibn Hajar and "Siyar A'lam al-Nubala'" by Al-Dhahabi.