Etchū Province
Matsukura Castle was built around the year 1335 by the Bōmon clan, and later came under the control of the Momonoi clan. By the Nanboku-chō period, it became the main base of Shiina clan. The Shiina served as retainers of the Hatakeyama clan, and were appointed "shugodai" of Niikawa District of Etchū Province. Their main rivals were the Jinbō clan based at Toyama Castle. In the 1550s, the Jinbō clan gained ascendant over the Shiina; however, the Shiina made an alliance with Uesugi Kenshin, who captured Toyama Castle in 1570 after a fierce back-and-forth struggle. The leader of the Jinbō clan fled to Oda Nobunaga, and the Toyama area was awarded to one of Kenshin's retainers. Furious that they had been denied the Toyama are, the Shiina turned to Kenshin's rival, Takeda Shingen, for assistance in 1568. Kenshin then laid siege to Matsukura Castle, which held out for two years until 1571. Shine Yasutane escaped, and continued to fight the Uesugi until his death in 1576. Uesugi Kenshin rebuilt Matsukura Castle as a base of operations in Etchū Province and expanded his territory westward, coming into conflict with Oda Nobunaga. However, he fell ill and died in 1578, and the Oda army led by Shibata Katsuie overran Kaga and Noto Provinces by the end of 1580, and all of Etchū Province with the exception of the Uozu area by 1581. The Uesugi strengthened Matsukura Castle as part for their final defensive line.