The caliph was assassinated on27th Zilhaj, 644 by a Magian while he was leading the prayer, stabbing him six times in the belly that proved fatal. The great caliph of Islam embraced martyrdom on 1st Moharram.
Hazrat Umar (RA) conquered 2,200,000 square miles of territory within the same period.
The verses recited before Hazrat Umar (R.A) were from SurahTaha or Surah Al-Hadid. After this, Hazrat Umar (R.A) rushed directly to the Holy Prophet (PBUH) with the same sword he had intended to kill him with. However, instead, he accepted Islam.