Complex sentence: Abdullah held important political posts throughout most of his adult life; he became mayor of Mecca as a young man and in 1962 he was appointed commander of the Saudi Arabian National Guard, a post he was still holding when he became king.
Split into simpler sentences: Abdullah held important political posts throughout most of his adult life. And, in 1962, he was appointed commander of the Saudi Arabian National Guard, a post he was still holding when he became king.