Complex sentence: In May 1990 the position was re-titled to its current name with the now-Lieutenant General Choo still in office, having been promoted to each of the general ranks in 1974,1978 and 1988.
Split into simpler sentences: In May 1990 the position was re-titled to its current name, with Choo, now a Lieutenant-General, still in office. He had been promoted to each of the general ranks in 1974,1978 and 1988.