Complex sentence: His eldest son Toshinaga participated in the Battle of Sekigahara and built Kanazawa Castle; he was noted for being the wealthiest daimyo in Tokugawa Japan with over 1.2 million "koku" (Turnbull, 1998).
Split into simpler sentences: His eldest son Toshinaga participated in the Battle of Sekigahara and built Kanazawa Castle. He is also noted for being the wealthiest daimyo in Tokugawa Japan with over 1.2 million "koku" (Turnbull, 1998).