Complex sentence: The president realized he now needed a Secretary that had the confidence of all three services, preferably one with significant military experience and within three months of the start of the conflict Johnson was dismissed from his position as Secretary of Defense.
Split into simpler sentences: The president realized he now needed a Secretary that had the confidence of all three services, preferably one with significant military experience. Within three months of the start of the conflict Johnson was dismissed from his position as Secretary of Defense.