Complex sentence: The battle fleet sortie concept was very similar in concept to that intended by the late Admiral Yamamoto in the battle of Midway, as is no surprise as many of the officers planning that were still on the General Staff of the Combined Fleet.
Split into simpler sentences: The battle fleet sortie concept was very similar to that intended by the late Admiral Yamamoto in the battle of Midway. Many of the officers who had planned Midway were still on the General Staff of the Combined Fleet.