Reddit mentions of War in Japan 1467–1615 (Essential Histories)

Clavell's Shogun is loosely based on actual history. Very, very loosely. Decades of history are blended together, and various historical figures are conflated into new characters. It's not even close to an accurate reflection of the political and cultural situation at the time, and of course it shoves in a white guy hero... Yeah, it's an entertaining read, but it also tends to make historians froth at the mouth.

The issue with ninjas is that most of the ninja mythology was invented during the 1800s... a good 200 years after the end of the "Warring States" period when much of this ninja action supposedly took place. A whole slew of popular novels were written featuring Sanada Yukimura (a samurai commander known for his cunning tactics) and his "Ten Braves," who were all legendary ninja. Sarutobi Sasuke is probably the most famous of the Ten Braves. Although Sanada Yukimura and the Ten Braves ultimately lost to Tokugawa Ieyasu (whose dynasty would rule Japan for the next 250 years), they were made out to be folk heroes with almost supernatural skill and cleverness.

...However, there's virtually zero evidence that any of these ninja ever existed outside of novels. The whole "ninja" mythos was invented in the 1800s, partly because it sounded cool and partly because the descendents of Sanada's samurai compatriots had suffered two hundred years of oppression under the ruling (but declining) Tokugawa regime, so there was still plenty of simmering resentment. Those two factors together sold a hell of a lot of books.

Samurai did use spies and saboteurs, but they weren't dudes who ran around in black Cobra Kai outfits slinging shuriken at each other. They were basically normal samurai. Political tensions were high during the Warring States era, but most samurai were surprisingly blatant about their backstabbing. Why go through the trouble of using ninja when you can simply lie, bribe, and threaten your way into power?

The biggest influence on modern ideas about ninja was actually the theatre. Kabuki stage plays and bunraku puppet plays both make use of stagehands who dress all in black and cover their faces with black cloth. Since the actors were brightly dressed and painted, these black-clad stagehands were "invisible." So a "ninja" character could creep around the stage in a stagehand's uniform, totally ignored by the audience until they revealed themselves.

Anyway, you were asking for books! The real history of the samurai is, at least to me, much more interesting than made-up ninja stories. It's full of power struggles and epic battles and tragic miscalculations and dirty tactics. It's good stuff. If you're interested, I highly recommend basically anything by Stephen Turnbull. He's written several visual guides to major battles of the samurai era, with tons of illustrations and analysis. He even has a book on ninja, although as I mentioned, ninja are a pretty contentious point among Japanese historians and any modern "ninja training school" that claims authenticity is full of pure bullshit.

Turnbull's War in Japan 1467-1615 is a good place to start. Osaka 1616 and Sekigahara 1600 (by Anthony Bryant) are the real source for Clavell's "Shogun" novel. Europeans actually did have a pretty significant role in Japan's civil wars, but not to the romanticized extent of "Shogun."

Those are probably the most accessible and easy-to-read books on the Warring States era. Taiko by Eiji Yoshikawa is a semi-fictionalized but very well researched novel that covers some of the same time period, but it's a much more challenging read. Most of the other academic books I have are pretty dry, so start with Turnbull for the fully illustrated action version~

I read https://www.amazon.com/War-Japan-1467-1615-Essential-Histories/dp/1841764809 , and that's how I got into it, but people seem to like https://www.amazon.com/Sengoku-Jidai-Nobunaga-Hideyoshi-Ieyasu-ebook/dp/B078X3MVBL , although I've never read it. Actually, this is one of those rare moments when I will vouch for YouTube channels like Extra Credits ( https://www.youtube.com/watch?v=hDsdkoln59A). It's a great and insightful overview to start with, and then go to the books for details.

From a military history standpoint, Stephen Turnbull's War In Japan is good. Very much focused on battles and wars rather than more general history, but good for what it covers.

For a more lower level sort of look at the period, The Culture of Civil War in Kyoto is good. It looks not so much at grand battles and strategies and focuses more on how the wars actually impacted life for people.

I've got a couple suggestions for you:

First up is a historical fiction called the Samurai's Tale by Erik Haugaar. This story covers a young Uesugi retainer who is taken in by the Takeda after his clan is bested in a battle and details his rise from the ranks to becoming a low ranked retainer for the Takeda. Ends right around the Battle of Nagashino and the fall of Takeda Katsuyori (https://www.amazon.com/Samurais-Tale-Erik-C-Haugaard/dp/0618615121)

The second one is War in Japan 1467 - 1615 by Stephen Turnbull. This one is a non-fiction that covers from the Onin War all the way up to the Siege of Osaka, ending the Sengoku Jidai. This was required reading in a Japanese history course I took. It covers a pretty broad range so it doesn't go over anything too thoroughly, but I think it'll be a good primer for you (https://www.amazon.com/War-Japan-1467-1615-Essential-Histories/dp/1841764809)

Happy studying!