Complex sentence: An outstanding tactician, he was made all the more iconic for his missing eye, having smallpox at the age of 6 it attacked his eye and would've kill hadn't Date Masamune gouged out his own eye.
Split into simpler sentences: An outstanding tactician, he was made all the more iconic for his missing eye. A case of smallpox attacked his eye and would have killed had Date Masamune not gouged out his own eye.