Nagahide Niwa was one of the Oda and Toyotomi reatainers. He served as a retainer to the Oda clan, and was eventually a daimyo in his own right.
Nagahide was one of Nobunaga Oda's chief retainers. He married Nobunaga's niece and received the fief of Sawayama in Omi worth 50,000 koku. Nagahide was present at many of Nobunaga's battles including Anegawa in 1570, Nagashino in 1575, the Honganji Campaign from 1570-1580, Tedorigawa in 1577, and the Second Invasion of Iga in 1581 and was named one of the administrators of Kyoto after Nobunaga entered that city in 1568. Nagahide constracted the castle of Azuchi for Nobunaga and as a reward he received the fief of Obama in Wakasa worth 100,000 koku.In 1582 was given the honor of riding at the head of Nobunaga's army in a parade in Kyoto. In the fifth month of that year he was ordered to accompany Nobutaka Oda in the invasion of Shikoku. When Nobunaga was killed the next month, he joined Hideyoshi's army in Osaka and took part in the Battle of Yamazaki. Nagahide was essentially neutral during Hideyoshi Toyotomi's war with Katsuie Shibata, but did support the former the next year, marching against Narimasa Sassa during the Komaki Campaign.