Kawanakajima is the area where Chikuma River and Sai River meet. It was very important transit spots which connect to Echigo, Kozuke, and Kai.
History
1st battle: the Battle of Fuse in 1553
2nd battle: the Battle of Sai River in 1555
3rd battle: the Battle of Uenohara in 1557
4th battle: the Battle of Hachimanbara in 1561
5th battle: the Battle of Shiozaki in 1564
The reason why they fought 5 times?
Kawanakajima was very famous for double cropping area which produce a large amount of food. Especially, Kai, the land of Takeda Shingen, couldn't produce much rice. Shingen really need Kawanakajima for his large army. Uesugi Kenshin's aunt was wife of Takanashi Masayori who was the feudal lord of North Shinano. To help his relatives and prevent Shingen to expand his land to Echigo, Kenshi also had to keep this land.
The 2nd Battle: the Battle of Sai River
2nd and 4th Battle of Kawanakajima are actually considered as the real battle happened at Kawanakajima between Takeda Shingen and Uesugi Kenshin.
The Battle of Sai River happened in 1555. Shingen and Kenshin fought about 200 days in this battle from April to October. In October 15, Imagawa Yoshimoto intermediated them and made a deal that Kenshin kept the area around Zenkoji Hills, and Shingen kept lest of Shinano.
The 4th Battle: the Battle of Hachimanbara
The Battle of Hachimanbara is what people consider of the Battle of Kawanakajima. It happend in 1561. The battle of Hachimanbara is the only the major battle, which they fought and lost many men, happened at Kawanakajima. In this battle, Shingen had 20,000 soldiers, and Kenshi had 18,000 armies. After the battle, both Shingen and Kenshin lost over 4,000 soldiers. It was the toughest battle ever happened in the history of Japan.
This famous battle is actually fiction made in Edo Period. "Koyogunkan" is the one of the major book, and most of the story written and known today is basted on this book. However, there is no historical record or evidence of how the actual battle was happened. The battle itself happened for sure because there are many letters of Shingen and Kenshin mentioned about this battle, and the record of Myohoji Temple also describe about this battle.
In August 15, Kenshin arrived at Zenkoji Temple and left his baggage crews and 5,000 soldiers at the temple. Then, he took 13,000 soldiers and set his headquarters at Mt. Saijo in August 16.
Shingen arrived in August 24 with 20,000 soldiers at Mt. Chausu, and moved his army to Kaizu Castle in 29. Kenshin had a chance to defeat Kaizu Castle (Matsushiro castle), but because Kenshin stayed with Samurai honest or maybe he was not good defeating castle, he stayed at the mountain and never attacked the castle. Also, Mt. Saijo is the dead end spots. This is biggest mystery why Kenshin settled his base on Mt. Saijo.
They spend 10 days for looking each other, Yamamoto Kansuke and Baba Nobuharu offered the plan to attack Kenshin. Shingen took the strategy of them and started attacking Kenshin. In September 10, Shingen divided his army half. 12,000 soldiers started attacking the mountain, and moved lest of his soldiers at Hachimanbara. The mission of 12,000 army was draw Kenshin from the mountain, and trapped them in the field. He moved this army before the sunrise. However, Kenshin found out that Shingen ’s plan and trapped him back. Kenshin emptied his army from the mountain and get down silently from the mountain. Kenshin was trying to make a surprise attack.
There was deep fog happened at that day which helped Kenshin's surprise attack. Kenshin successfully attack Shingen's main base, and just about to kill him. That’s famous "Ikkiuchi fight of Shingen and Kenshin." However, Takeda Nobushige, the brother of Shingen, risked his life to help Shigen and stopped Kenshi for a while until the dived army arrived back from the mountain. At the noon, the other half of Shingen's army was back from the mountain, and Kenshin had to pull back to Zenkoji Temple.
The story said, in this battle, Kenshin won the first half of the battle, and Shingen won the last half of the battle. This famous story is all fiction made in Edo Period. However, the record said there was a big battle happened that day. Kenshin lost the control of North Nagano after this battle. It makes Shingen winner, but Shingen lost so many his important samurai such as his brother, Nobushige, Yamamoto Kansuke, Morozumi Toramitsu and more. This lost of Shingen immediately coursed the fall of Takeda clan. So, Shingen was not winner either.