He married Oda Nobunaga's sister Ichi but later joined the Asakura family and the monks of Mt. Hiei against Nobunaga. Nagamasa was defeated by Oda and Tokugawa Ieyasu at the battle of Anegawa in 1570.
In 1573, Oda laid siege to Nagamasa's castle at Odani. Unfortunately for Nagamasa, he was there at the time. He committed suicide and in exchange, Oda spared Nagamasa's family (which of course included his--Nobunaga's--own sister).
Three of Nagamasa's daughters are famous for marrying famous men.
The article is originally from OpenHistory.