The description of the Battle of Kawanakajima given in the first episode of the Mirage of Blaze anime offends me sufficiently that I will babble a more historically accurate (or at least, detailed) version. This is primarily based off of the information from Stephen Turnbull. Turnbull is my favorite reference on Japanese military history, and I trust his research enough that I will 1) trust his version of events as being as accurate as historically possible and will frequently skip doing any secondary research to confirm accuracy or try to find discrpencies, and 2) will trust his research over that of most Japanese sources. Why? Because the Japanese sources I see don't always list references and Turnbull always does. And in the case of Kawanakajima, he lists the Kouyou Gunkan as one of his references. Kouyou Gunkan is attributed to one Kousaka Danjou Masanobu, who was one of the principle generals involved in the fourth battle of Kawanakajima. Turnbull is my researchy hero!
(For those who have seen MoB, yes, that would be THAT Kousaka. Busy poofta, huh?)
Anyway, on with the history...
"The Battle of Kawanakajima" is a bit of a misnomer, since there were five seperate battles fought at Kawanakajima. Given the number of battles this is obviously a location of great stratgic importance. These days it is a suburb of Nagano (made famous for the 2002 winter Olympics), but back in the Sengoku period it was very strategic, since it controlled communications for the mountain passes to the south and the (for that area) large plain to the north. It was a key point to Takeda defense against incursions from the Uesugi from the north/north-east.
All of the Battles of Kawanakajima featured the same two principle daimyou, Takeda Shingen and Uesugi Kenshin. Both men are famous in Japanese history for being excellent strategists. They lived in the heart of the Warring States period, and were respected as some of the best generals of the time -- in a time known for its excellent generals. Which says something about their talents.
Usually when "the Battle of Kawanakajima" is referenced, it refers to the fourth battle. The first two battles were rather like watching a pair of kendo masters fighting: An awful lot of staring intently, unmoving, until both sides realize that there is no way for them to win and decamp. Casualties from these battles were minimal, and the battles ended essentially in stalemate. The third battle involved a lot of Shingen wandering around taking territory until Kenshin decided he was tired of that and sent a force into the field. At that point, Shingen withdrew. So not a lot was accomplished there, either.
The fourth battle makes up for all of that. It ended up having the highest casualty rate of any battle in the Sengoku period (one of Japan's bloodiest periods), with the victor escaping with a "mere" 62% casualty rate and the "loser" suffering 72% losses. This, in a time where 20% was more normal. *ouch* And even after that they decided to fight there again? O.O
Anyway, it started in September of 1561. (Dammit, after all my praise of Turnbull what do I find but an error? He lists the battle as starting in 1461. Which would be difficult, since Shingen wasn't born until 1521 and Kenshin nine years later. I took the liberty of -- after researching it properly, thankyouverymuch -- correcting the century to the obvious one. Turnbull, how could you betray me? *sob*)
*ahem* Research hysteria over, we are back to the main story. Which starts in September, 1561. Kenshin decided that he was going to do away with Shingen once and for all, and to that end he marched a force of 18,000 to Saijouyama, a hill near by the Takeda fort, Kaizuru Castle. At this point, taking the castle would have been easy, since, while it was commanded by Kousaka Danjou Masanobu, one of the Takeda Twenty-four Generals, it also only had a garrison of 150. Fortunately for Kousaka and his men, Kenshin's main purpose in moving into the neighborhood wasn't to take the castle. He wanted to lure Shingen into a battle. Some people send invites, some people send roses. Kenshin sent an army.
Using a system of signal flares Kousaka Danjou sent a message to Shingen, who responded as expected by setting out immediately at the head of an army of 16,000 men. Since continuing to hold that position was of critical importance to him, Shingen took personal command of the army. Meanwhile, Takeda troops from elsewhere in the region joined with the main force, bringing the total up to 20,000
There is one other major feature of the terrain that is pertient to the story, which is a riverIt's located near Saijouyama, and has two fords in the area. Shingen's army marched keeping the river in between them and Kenshin's army at Saijouyama. They crossed at the downstream ford, and entered Kaizu Castle.
The two armies sat there for a few days. Then...
Shingen's plan was analogous to the way that a woodpecker taps on the bark of a tree to scare the insects out, then gobbles them up. Under the cover of darkness he would send half his army back across the river (using the same downriver ford he used earlier) to the wide plain to the north, and would arrange them in a wide formation roughly perpendicular to the river. The other half of his army would sneak out -- also under cover of darkness -- of Kaizu Castle and go up the back side of the hill the Uesugi army was camped on. Come daylight, the troops on Saijouyama would attack the Uesugi force and drive them across the river, where the other half of the army would be waiting for them. Gunning and cutting down the disorderly, retreating Uesugi army should be no problem.
There was, of course, a problem. Shingen moved his half of the army out of the castle and across the river starting at midnight. The troop movements were observed by Uesugi spies who reported their observations to Kenshin. Being the strategic genius that he was, Kenshin figured out what Shingen's intent was and devised a counter-plan. Also under the cover of darkness he moved his entire army off of Saijouyama, across the upstream ford and into position to be ready to meet the half of Shingen's army come morning.
Let's take a minute and do some math. Kenshin brought a force of 18,000. Shingen had 20,000 to begin with, which he then split in half. The 10,000 Takeda men on the north bank of the river were expecting to see a disarrayed army retreating across their front. When the sun rose, instead what appeared in front of them out of the mist was a huge, well-organized force marching straight at them. Not quite the right start to the day for them.
Shingen's younger brother was killed pretty much immediately by the vanguard forces, led by a certain Kakizaki Haruie. The Uesugi forces were well organized, and imployed a wheel-shaped formation which allowed fresh troops to be rotated in and tired troops to move out of the fighting. Things went badly for the Takeda forces.
Well, for half of them, at any rate. Remember, the other half were stealthily sneaking up behind Uesugi forces on Saijouyama. They didn't know that the Uesugi army had moved off in the middle of the night. They arrived at where they expected to be an army sitting at unawares, found nothing, and knew that something was up. Hearing sounds of battle, they rushed to the closest ford, which was the upstream one -- the same one that the Uesugi army had used in the night.
As seen earlier, Kenshin was no fool. Figuring that he needed to keep an avenue of retreat open, he left a force of 3,000 to defend the ford. Which is all well and good, except they faced a force of 10,000 coming at them. The fighting here was fierce, but in the end the Takeda forces -- led by Kousaka Danjou eventually prevailed through numerical superiority and were able to cross the river.
The observant will note that at this point, the battlefield exactly resembled a much more disordered version of Shingen's original "woodpecker attack" plan. The Uesugi army was caught between the two halves of the Takeda army, and suddenly the tables were turned. After some fighting the Uesugi retreated toward Zenkouji Temple (the most famous temple in Nagano, which was, at that time, essentially an Uesugi holding.) Shingen's forces had been decimated enough that they did not offer pursuit, and a cease-fire ensued. The "losing" Uesugi army lost around 11,500 men, while the "winning" Takeda army lost 12,400. (The percentage lost might have been lower on the Takeda side, but they started out with more troops to begin with.)
There are two incidents of note that took place during the battle. The first involves the general who conceived of the "woodpecker" plan in the first place, Yamamoto Kansuke. When the Uesugi attack first started and was chewing through the Takeda forces, Kansuke decided that he must pay for the failure of his plan in the traditional samurai way. Taking his spear he charged a section of the Uesugi offensive. While he did a lot of damage to the enemy, they returned the favor. Wounded in many places, he retreated to a near-by grassy knoll and slit his belly.
The other incident is the stuff of which samurai legends are made, and may be apocraphal. Before the rescuing force led by Kousaka Danjou joined the fray, things went so badly for the Takeda forces that the Uesugi army reached Shingen's command post. According to legend, Kenshin himself rode into the camp and personally attacked Shingen. Left without even time to draw his sword, Shingen defended himself from Kenshin's attack with his war fan. This would sound like a rather flimsy defence, except that war fans were made with steel ribs. Their primary purpose was for signaling -- but they obviously could be used for defence in a pinch. According to the Kouyou Gunkan, Shingen received three blows to his armour and seven to his war fan before one of his retainers was able to drive Kenshin off. It's hard to say if this incident actually took place, but it sure makes good (samurai) drama.
The fifth Battle of Kawanakajima was understandably a good deal less eventful. It featured both armies staring at each other, broken by occasional skirmishing, for about 60 days. After that time both sides retreated. After that both Kenshin and Shingen get distracted by, well, easier to defeat fish and never fought at Kawanakajima again.