Complex sentence: In 1955 he was called on to succeed Kailash Nath Katju as Home Minister; in that position, his chief achievement was the establishment of Hindi as an official language of the central government and a few states.
Split into simpler sentences: In 1955 he was called on to succeed Kailash Nath Katju as Home Minister;. As Home minister, his chief achievement was the establishment of Hindi as an official language of the central government and a few states.